Displaying publications 1 - 20 of 44 in total

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  1. Glycoproteomics-based liquid biopsy: translational outlook for colorectal cancer clinical management in Southeast Asia
    Kumarasamy G, Mohd Salim NH, Mohd Afandi NS, Hazlami Habib MA, Mat Amin ND, Ismail MN, et al.
    Future Oncol, 2023 Nov;19(34):2313-2332.
    PMID: 37937446 DOI: 10.2217/fon-2023-0704
    Colorectal cancer (CRC) signifies a significant healthcare challenge in Southeast Asia. Despite advancements in screening approaches and treatment modalities, significant medical gaps remain, ranging from prevention and early diagnosis to determining targeted therapy and establishing personalized approaches to managing CRC. There is a need to expand more validated biomarkers in clinical practice. An advanced technique incorporating high-throughput mass spectrometry as a liquid biopsy to unravel a repertoire of glycoproteins and glycans would potentially drive the development of clinical tools for CRC screening, diagnosis and monitoring, and it can be further adapted to the existing standard-of-care procedure. Therefore this review offers a perspective on glycoproteomics-driven liquid biopsy and its potential integration into the clinical care of CRC in the southeast Asia region.
    Matched MeSH terms: Protein Processing, Post-Translational
  2. Fulltext Self-Adaptive Filtering Approach for Improved Indoor Localization of a Mobile Node with Zigbee-Based RSSI and Odometry
    Loganathan A, Ahmad NS, Goh P
    Sensors (Basel), 2019 Nov 01;19(21).
    PMID: 31683837 DOI: 10.3390/s19214748
    This study presents a new technique to improve the indoor localization of a mobile node by utilizing a Zigbee-based received-signal-strength indicator (RSSI) and odometry. As both methods suffer from their own limitations, this work contributes to a novel methodological framework in which coordinates of the mobile node can more accurately be predicted by improving the path-loss propagation model and optimizing the weighting parameter for each localization technique via a convex search. A self-adaptive filtering approach is also proposed which autonomously optimizes the weighting parameter during the target node's translational and rotational motions, thus resulting in an efficient localization scheme with less computational effort. Several real-time experiments consisting of four different trajectories with different number of straight paths and curves were carried out to validate the proposed methods. Both temporal and spatial analyses demonstrate that when odometry data and RSSI values are available, the proposed methods provide significant improvements on localization performance over existing approaches.
    Matched MeSH terms: Protein Processing, Post-Translational
  3. Fulltext Circadian Rhythm Disruption and Alzheimer's Disease: The Dynamics of a Vicious Cycle
    Sharma A, Sethi G, Tambuwala MM, Aljabali AAA, Chellappan DK, Dua K, et al.
    Curr Neuropharmacol, 2021;19(2):248-264.
    PMID: 32348224 DOI: 10.2174/1570159X18666200429013041
    All mammalian cells exhibit circadian rhythm in cellular metabolism and energetics. Autonomous cellular clocks are modulated by various pathways that are essential for robust time keeping. In addition to the canonical transcriptional translational feedback loop, several new pathways of circadian timekeeping - non-transcriptional oscillations, post-translational modifications, epigenetics and cellular signaling in the circadian clock - have been identified. The physiology of circadian rhythm is expansive, and its link to the neurodegeneration is multifactorial. Circadian rhythm disruption is prevelant in contamporary society where light-noise, shift-work, and transmeridian travel are commonplace, and is also reported from the early stages of Alzheimer's disease (AD). Circadian alignment by bright light therapy in conjunction with chronobiotics is beneficial for treating sundowning syndrome and other cognitive symptoms in advanced AD patients. We performed a comprehensive analysis of the clinical and translational reports to review the physiology of the circadian clock, delineate its dysfunction in AD, and unravel the dynamics of the vicious cycle between two pathologies. The review delineates the role of putative targets like clock proteins PER, CLOCK, BMAL1, ROR, and clock-controlled proteins like AVP, SIRT1, FOXO, and PK2 towards future approaches for management of AD. Furthermore, the role of circadian rhythm disruption in aging is delineated.
    Matched MeSH terms: Protein Processing, Post-Translational
  4. Functional Neuroproteomics: An Imperative Approach for Unravelling Protein Implicated Complexities of Brain
    Husain I, Ahmad W, Ali A, Anwar L, Nuruddin SM, Ashraf K, et al.
    CNS Neurol Disord Drug Targets, 2021;20(7):613-624.
    PMID: 33530918 DOI: 10.2174/1871527320666210202121624
    A proteome is defined as a comprehensive protein set either of an organ or an organism at a given time and under specific physiological conditions. Accordingly, the study of the nervous system's proteomes is called neuroproteomics. In the neuroproteomics process, various pieces of the nervous system are "fragmented" to understand the dynamics of each given sub-proteome in a much better way. Functional proteomics addresses the organisation of proteins into complexes and the formation of organelles from these multiprotein complexes that control various physiological processes. Current functional studies of neuroproteomics mainly talk about the synapse structure and its organisation, the major building site of the neuronal communication channel. The proteomes of synaptic vesicle, presynaptic terminal, and postsynaptic density, have been examined by various proteomics techniques. The objectives of functional neuroproteomics are: to solve the proteome of single neurons or astrocytes grown in cell cultures or from the primary brain cells isolated from tissues under various conditions, to identify the set of proteins that characterize specific pathogenesis, or to determine the group of proteins making up postsynaptic or presynaptic densities. It is usual to solve a particular sub-proteome like the heat-shock response proteome or the proteome responding to inflammation. Post-translational protein modifications alter their functions and interactions. The techniques to detect synapse phosphoproteome are available. However, techniques for the analysis of ubiquitination and sumoylation are under development.
    Matched MeSH terms: Protein Processing, Post-Translational/physiology
  5. Fulltext Computational identification of 4-carboxyglutamate sites to supplement physiological studies using deep learning
    Naseer S, Ali RF, Fati SM, Muneer A
    Sci Rep, 2022 01 07;12(1):128.
    PMID: 34996975 DOI: 10.1038/s41598-021-03895-4
    In biological systems, Glutamic acid is a crucial amino acid which is used in protein biosynthesis. Carboxylation of glutamic acid is a significant post-translational modification which plays important role in blood coagulation by activating prothrombin to thrombin. Contrariwise, 4-carboxy-glutamate is also found to be involved in diseases including plaque atherosclerosis, osteoporosis, mineralized heart valves, bone resorption and serves as biomarker for onset of these diseases. Owing to the pathophysiological significance of 4-carboxyglutamate, its identification is important to better understand pathophysiological systems. The wet lab identification of prospective 4-carboxyglutamate sites is costly, laborious and time consuming due to inherent difficulties of in-vivo, ex-vivo and in vitro experiments. To supplement these experiments, we proposed, implemented, and evaluated a different approach to develop 4-carboxyglutamate site predictors using pseudo amino acid compositions (PseAAC) and deep neural networks (DNNs). Our approach does not require any feature extraction and employs deep neural networks to learn feature representation of peptide sequences and performing classification thereof. Proposed approach is validated using standard performance evaluation metrics. Among different deep neural networks, convolutional neural network-based predictor achieved best scores on independent dataset with accuracy of 94.7%, AuC score of 0.91 and F1-score of 0.874 which shows the promise of proposed approach. The iCarboxE-Deep server is deployed at https://share.streamlit.io/sheraz-n/carboxyglutamate/app.py .
    Matched MeSH terms: Protein Processing, Post-Translational*
  6. Experimental data for the slug two-phase flow characteristics in horizontal pipeline
    Mohmmed AO, Nasif MS, Al-Kayiem HH
    Data Brief, 2018 Feb;16:527-530.
    PMID: 29270452 DOI: 10.1016/j.dib.2017.11.026
    The data presented in this article were the basis for the study reported in the research articles entitled "Statistical assessment of experimental observation on the slug body length and slug translational velocity in a horizontal pipe" (Al-Kayiem et al., 2017) [1] which presents an experimental investigation of the slug velocity and slug body length for air-water tow phase flow in horizontal pipe. Here, in this article, the experimental set-up and the major instruments used for obtaining the computed data were explained in details. This data will be presented in the form of tables and videos.
    Matched MeSH terms: Protein Processing, Post-Translational
  7. iGluK-Deep: computational identification of lysine glutarylation sites using deep neural networks with general pseudo amino acid compositions
    Naseer S, Ali RF, Khan YD, Dominic PDD
    J Biomol Struct Dyn, 2022;40(22):11691-11704.
    PMID: 34396935 DOI: 10.1080/07391102.2021.1962738
    Lysine glutarylation is a post-translation modification which plays an important regulatory role in a variety of physiological and enzymatic processes including mitochondrial functions and metabolic processes both in eukaryotic and prokaryotic cells. This post-translational modification influences chromatin structure and thereby results in global regulation of transcription, defects in cell-cycle progression, DNA damage repair, and telomere silencing. To better understand the mechanism of lysine glutarylation, its identification in a protein is necessary, however, experimental methods are time-consuming and labor-intensive. Herein, we propose a new computational prediction approach to supplement experimental methods for identification of lysine glutarylation site prediction by deep neural networks and Chou's Pseudo Amino Acid Composition (PseAAC). We employed well-known deep neural networks for feature representation learning and classification of peptide sequences. Our approach opts raw pseudo amino acid compositions and obsoletes the need to separately perform costly and cumbersome feature extraction and selection. Among the developed deep learning-based predictors, the standard neural network-based predictor demonstrated highest scores in terms of accuracy and all other performance evaluation measures and outperforms majority of previously reported predictors without requiring expensive feature extraction process. iGluK-Deep:Computational Identification of lysine glutarylationsites using deep neural networks with general Pseudo Amino Acid Compositions Sheraz Naseer, Rao Faizan Ali, Yaser Daanial Khan, P.D.D DominicCommunicated by Ramaswamy H. Sarma.
    Matched MeSH terms: Protein Processing, Post-Translational
  8. Signatures of gene expression, DNA methylation and microRNAs of hepatocellular carcinoma with vascular invasion
    Sulaiman SA, Abu N, Ab-Mutalib NS, Low TY, Jamal R
    Future Oncol, 2019 Aug;15(22):2603-2617.
    PMID: 31339048 DOI: 10.2217/fon-2018-0909
    Aim: Micro and macro vascular invasion (VI) are known as independent predictors of tumor recurrence and poor survival after surgical treatment of hepatocellular carcinoma (HCC). Here, we aimed to re-analyze The Cancer Genome Atlas of liver hepatocellular carcinoma datasets to identify the VI-expression signatures. Materials & methods: We filtered The Cancer Genome Atlas liver hepatocellular carcinoma (LIHC) datasets into three groups: no VI (NVI = 198); micro VI (MIVI = 89) and macro VI (MAVI = 16). We performed differential gene expression, methylation and microRNA analyses. Results & conclusion: We identified 12 differentially expressed genes and 55 differentially methylated genes in MAVI compared with no VI. The GPD1L gene appeared in all of the comparative analyses. Higher GPD1L expression was associated with VI and poor outcomes in the HCC patients.
    Matched MeSH terms: Protein Processing, Post-Translational
  9. Fulltext Proteomics of chondrogenesis: a review
    Tay, L.X.
    JUMMEC, 2015;18(1):1-8.
    MyJurnal
    Osteoarthritis (OA) affects millions of people worldwide with its irreversible destruction of articular cartilage. Recently, the potential of using chondrogenic differentiated multipotent mesenchymal stromal cells (cMSCs) for OA treatment is being assessed. Preliminary clinical studies have been encouraging. However current studies have also demonstrated that cMSCs are not biochemically and biomechanically identical to native articular chondrocytes (ACs). Thus, there is an urgent need for the implementation of proteomic applications as proteomics involve protein identification, relative quantification of proteins and studies of post-translational modification which reveal novel regulating processes of complex mechanisms such as in chondrogenesis. A comprehensive understanding of chondrogenesis is essential for the establishment of an effective cMSC model to regenerate cartilage. In this article, we will review current proteomic studies on chondrogenesis, focusing on recent findings and the proteomic approaches utilised.
    Matched MeSH terms: Protein Processing, Post-Translational
  10. Proteomics in Systems Biology
    Aizat WM, Hassan M
    Adv Exp Med Biol, 2018 11 2;1102:31-49.
    PMID: 30382567 DOI: 10.1007/978-3-319-98758-3_3
    Proteomics is the study of proteins, the workhorses of cells. Proteins can be subjected to various post-translational modifications, making them dynamic to external perturbation. Proteomics can be divided into four areas: sequence, structural, functional and interaction and expression proteomics. These different areas used different instrumentations and have different focuses. For example, sequence and structural proteomics mainly focus on elucidating a particular protein sequence and structure, respectively. Meanwhile, functional and interaction proteomics concentrate on protein function and interaction partners, whereas expression proteomics allows the cataloguing of total proteins in any given samples, hence providing a holistic overview of various proteins in a cell. The application of expression proteomics in cancer and crop research is detailed in this chapter. The general workflow of expression proteomics consisting the use of mass spectrometry instrumentation has also been described, and some examples of proteomics studies are also presented.
    Matched MeSH terms: Protein Processing, Post-Translational
  11. Fulltext Effect of Kelulut Honey on the Cellular Dynamics of TGFβ-Induced Epithelial to Mesenchymal Transition in Primary Human Keratinocytes
    Nordin A, Chowdhury SR, Saim AB, Bt Hj Idrus R
    Int J Environ Res Public Health, 2020 05 06;17(9).
    PMID: 32384749 DOI: 10.3390/ijerph17093229
    Over-induction of epithelial to mesenchymal transition (EMT) by tumor growth factor beta (TGFβ) in keratinocytes is a key feature in keloid scar. The present work seeks to investigate the effect of Kelulut honey (KH) on TGFβ-induced EMT in human primary keratinocytes. Image analysis of the real time observation of TGFβ-induced keratinocytes revealed a faster wound closure and individual migration velocity compared to the untreated control. TGFβ-induced keratinocytes also have reduced circularity and display a classic EMT protein expression. Treatment of 0.0015% (v/v) KH reverses these effects. In untreated keratinocytes, KH resulted in slower initial wound closure and individual migration velocity, which sped up later on, resulting in greater wound closure at the final time point. KH treatment also led to greater directional migration compared to the control. KH treatment caused reduced circularity in keratinocytes but displayed a partial EMT protein expression. Taken together, the findings suggest the therapeutic potential of KH in preventing keloid scar by attenuating TGFβ-induced EMT.
    Matched MeSH terms: Protein Processing, Post-Translational
  12. Fulltext Protein diversification through post-translational modifications, alternative splicing, and gene duplication
    Goldtzvik Y, Sen N, Lam SD, Orengo C
    Curr Opin Struct Biol, 2023 Aug;81:102640.
    PMID: 37354790 DOI: 10.1016/j.sbi.2023.102640
    Proteins provide the basis for cellular function. Having multiple versions of the same protein within a single organism provides a way of regulating its activity or developing novel functions. Post-translational modifications of proteins, by means of adding/removing chemical groups to amino acids, allow for a well-regulated and controlled way of generating functionally distinct protein species. Alternative splicing is another method with which organisms possibly generate new isoforms. Additionally, gene duplication events throughout evolution generate multiple paralogs of the same genes, resulting in multiple versions of the same protein within an organism. In this review, we discuss recent advancements in the study of these three methods of protein diversification and provide illustrative examples of how they affect protein structure and function.
    Matched MeSH terms: Protein Processing, Post-Translational
  13. Fulltext Ageing, Drosophila melanogaster and Epigenetics
    Halim MA, Tan FHP, Azlan A, Rasyid II, Rosli N, Shamsuddin S, et al.
    Malays J Med Sci, 2020 May;27(3):7-19.
    PMID: 32684802 MyJurnal DOI: 10.21315/mjms2020.27.3.2
    Ageing is a phenomenon where the accumulation of all the stresses that alter the functions of living organisms, halter them from maintaining their physiological balance and eventually lead to death. The emergence of epigenetic tremendously contributed to the knowledge of ageing. Epigenetic changes in cells or tissues like deoxyribonucleic acid (DNA) methylation, modification of histone proteins, transcriptional modification and also the involvement of non-coding DNA has been documented to be associated with ageing. In order to study ageing, scientists have taken advantage of several potential organisms to aid them in their study. Drosophila melanogaster has been an essential model in establishing current understanding of the mechanism of ageing as they possess several advantages over other competitors like having homologues to more than 75% of human disease genes, having 50% of Drosophila genes are homologues to human genes and most importantly they are genetically amenable. Here, we would like to summarise the extant knowledge about ageing and epigenetic process and the role of Drosophila as an ideal model to study epigenetics in association with ageing process.
    Matched MeSH terms: Protein Processing, Post-Translational
  14. Fulltext Proteolytic cleavage analysis at the Murray Valley encephalitis virus NS1-2A junction
    Addis SN, Lee E, Bettadapura J, Lobigs M
    Virol J, 2015;12:144.
    PMID: 26377679 DOI: 10.1186/s12985-015-0375-4
    Our understanding of the proteolytic processing events at the NS1-2A junction in the flavivirus polyprotein has not markedly progressed since the early work conducted on dengue virus (DENV). This work identified an octapeptide sequence located immediately upstream of the cleavage site thought to be important in substrate recognition by an as yet unknown, endoplasmic reticulum-resident host protease. Of the eight amino acid recognition sequence, the highly conserved residues at positions P1, P3, P5, P7 and P8 (with respect to N-terminus of NS2A) are particularly sensitive to amino acid substitutions in terms of DENV NS1-NS2A cleavage efficiency; however, the role of the octapeptide in efficient NS1 and NS2A production of other flaviviruses has not been experimentally addressed.
    Matched MeSH terms: Protein Processing, Post-Translational*
  15. Unrestrictive identification of post-translational modifications in Hevea brasiliensis latex
    Habib MAH, Gan CY, Abdul Latiff A, Ismail MN
    Biochem. Cell Biol., 2018 12;96(6):818-824.
    PMID: 30058361 DOI: 10.1139/bcb-2018-0020
    The natural rubber latex extracted from the bark of Hevea brasiliensis plays various important roles in modern society. Post-translational modifications (PTMs) of the latex proteins are important for the stability and functionality of the proteins. In this study, latex proteins were acquired from the C-serum, lutoids, and rubber particle layers of latex without using prior enrichment steps; they were fragmented using collision-induced dissociation (CID), higher-energy collisional dissociation (HCD), and electron-transfer dissociation (ETD) activation methods. PEAKS 7 were used to search for unspecified PTMs, followed by analysis through PTM prediction tools to crosscheck both results. There were 73 peptides in 47 proteins from H. brasiliensis protein sequences derived from UniProtKB were identified and predicted to be post-translationally modified. The peptides with PTMs identified include phosphorylation, lysine acetylation, N-terminal acetylation, hydroxylation, and ubiquitination. Most of the PTMs discovered have yet to be reported in UniProt, which would provide great assistance in the research of the functional properties of H. brasiliensis latex proteins, as well as being useful biomarkers. The data are available via the MassIVE repository with identifier MSV000082419.
    Matched MeSH terms: Protein Processing, Post-Translational/physiology
  16. Humanizing glycosylation pathways in eukaryotic expression systems
    Khan AH, Bayat H, Rajabibazl M, Sabri S, Rahimpour A
    World J Microbiol Biotechnol, 2017 Jan;33(1):4.
    PMID: 27837408
    Glycosylation represents the most widespread posttranslational modifications, found in a broad spectrum of natural and therapeutic recombinant proteins. It highly affects bioactivity, site-specificity, stability, solubility, immunogenicity, and serum half-life of glycoproteins. Numerous expression hosts including yeasts, insect cells, transgenic plants, and mammalian cells have been explored for synthesizing therapeutic glycoproteins. However, glycosylation profile of eukaryotic expression systems differs from human. Glycosylation strategies have been proposed for humanizing the glycosylation pathways in expression hosts which is the main theme of this review. Besides, we also highlighted the glycosylation potential of protozoan parasites by emphasizing on the mammalian-like glycosylation potential of Leishmania tarentolae known as Leishmania expression system.
    Matched MeSH terms: Protein Processing, Post-Translational*
  17. Fulltext Histone deacetylase inhibitors as potential treatment for spinal muscular atrophy
    Mohseni J, Zabidi-Hussin ZA, Sasongko TH
    Genet Mol Biol, 2013 Sep;36(3):299-307.
    PMID: 24130434 DOI: 10.1590/S1415-47572013000300001
    Histone acetylation plays an important role in regulation of transcription in eukaryotic cells by promoting a more relaxed chromatin structure necessary for transcriptional activation. Histone deacetylases (HDACs) remove acetyl groups and suppress gene expression. HDAC inhibitors (HDACIs) are a group of small molecules that promote gene transcription by chromatin remodeling and have been extensively studied as potential drugs for treating of spinal muscular atrophy. Various drugs in this class have been studied with regard to their efficacy in increasing the expression of survival of motor neuron (SMN) protein. In this review, we discuss the current literature on this topic and summarize the findings of the main studies in this field.
    Matched MeSH terms: Protein Processing, Post-Translational
  18. Fulltext Stable heterologous expression of biologically active terpenoids in green plant cells
    Ikram NK, Zhan X, Pan XW, King BC, Simonsen HT
    Front Plant Sci, 2015;6:129.
    PMID: 25852702 DOI: 10.3389/fpls.2015.00129
    Plants biosynthesize a great diversity of biologically active small molecules of interest for fragrances, flavors, and pharmaceuticals. Among specialized metabolites, terpenoids represent the greatest molecular diversity. Many terpenoids are very complex, and total chemical synthesis often requires many steps and difficult chemical reactions, resulting in a low final yield or incorrect stereochemistry. Several drug candidates with terpene skeletons are difficult to obtain by chemical synthesis due to their large number of chiral centers. Thus, biological production remains the preferred method for industrial production for many of these compounds. However, because these chemicals are often found in low abundance in the native plant, or are produced in plants which are difficult to cultivate, there is great interest in engineering increased production or expression of the biosynthetic pathways in heterologous hosts. Although there are many examples of successful engineering of microbes such as yeast or bacteria to produce these compounds, this often requires extensive changes to the host organism's metabolism. Optimization of plant gene expression, post-translational protein modifications, subcellular localization, and other factors often present challenges. To address the future demand for natural products used as drugs, new platforms are being established that are better suited for heterologous production of plant metabolites. Specifically, direct metabolic engineering of plants can provide effective heterologous expression for production of valuable plant-derived natural products. In this review, our primary focus is on small terpenoids and we discuss the benefits of plant expression platforms and provide several successful examples of stable production of small terpenoids in plants.
    Matched MeSH terms: Protein Processing, Post-Translational
  19. Potential application of Leishmania tarentolae as an alternative platform for antibody expression
    Lai JY, Klatt S, Lim TS
    Crit Rev Biotechnol, 2019 May;39(3):380-394.
    PMID: 30720351 DOI: 10.1080/07388551.2019.1566206
    Through the discovery of monoclonal antibody (mAb) technology, profound successes in medical treatment against a wide range of diseases have been achieved. This has led antibodies to emerge as a new class of biodrugs. As the "rising star" in the pharmaceutical market, extensive research and development in antibody production has been carried out in various expression systems including bacteria, insects, plants, yeasts, and mammalian cell lines. The major benefit of eukaryotic expression systems is the ability to carry out posttranslational modifications of the antibody. Glycosylation of therapeutic antibodies is one of these important modifications, due to its influence on antibody structure, stability, serum half-life, and complement recruitment. In recent years, the protozoan parasite Leishmania tarentolae has been introduced as a new eukaryotic expression system. L. tarentolae is rich in glycoproteins with oligosaccharide structures that are very similar to humans. Therefore, it is touted as a potential alternative to mammalian expression systems for therapeutic antibody production. Here, we present a comparative review on the features of the L. tarentolae expression system with other expression platforms such as bacteria, insect cells, yeasts, transgenic plants, and mammalian cells with a focus on mAb production.
    Matched MeSH terms: Protein Processing, Post-Translational/genetics
  20. Characterization of Chlamydomonas Ribulose-1,5-bisphosphate carboxylase/oxygenase variants mutated at residues that are post-translationally modified
    Rasineni GK, Loh PC, Lim BH
    Biochim Biophys Acta Gen Subj, 2017 Feb;1861(2):79-85.
    PMID: 27816753 DOI: 10.1016/j.bbagen.2016.10.027
    BACKGROUND: Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the chloroplast enzyme that fixes CO2 in photosynthesis, but the enzyme also fixes O2, which leads to the wasteful photorespiratory pathway. If we better understand the structure-function relationship of the enzyme, we might be able to engineer improvements. When the crystal structure of Chlamydomonas Rubisco was solved, four new posttranslational modifications were observed which are not present in other species. The modifications were 4-hydroxylation of the conserved Pro-104 and 151 residues, and S-methylation of the variable Cys-256 and 369 residues, which are Phe-256 and Val-369 in land plants. Because the modifications were only observed in Chlamydomonas Rubisco, they might account for the differences in kinetic properties between the algal and plant enzymes.

    METHODS: Site-directed mutagenesis and chloroplast transformation have been used to test the essentiality of these modifications by replacing each of the residues with alanine (Ala). Biochemical analyses were done to determine the specificity factors and kinetic constants.

    RESULTS: Replacing the modified-residues in Chlamydomonas Rubisco affected the enzyme's catalytic activity. Substituting hydroxy-Pro-104 and methyl-Cys-256 with alanine influenced Rubisco catalysis.

    CONCLUSION: This is the first study on these posttranslationally-modified residues in Rubisco by genetic engineering. As these forms of modifications/regulation are not available in plants, the modified residues could be a means to modulate Rubisco activity.

    GENERAL SIGNIFICANCE: With a better understanding of Rubisco structure-function, we can define targets for improving the enzyme.

    Matched MeSH terms: Protein Processing, Post-Translational/genetics*
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