Malonylome Analysis Reveals the Involvement of Lysine Malonylation in Metabolism and Photosynthesis in Cyanobacteria

Nutraceutical prospects of genetically engineered cyanobacteria- technological updates and significance

Genetically engineered cyanobacterial strains that have improved growth rate, biomass productivity, and metabolite productivity could be a better option for sustainable bio-metabolite production. The global demand for biobased metabolites with nutraceuticals and health benefits has increased due to their safety and plausible therapeutic and nutritional utility. Cyanobacteria are solar-powered green cellular factories that can be genetically tuned to produce metabolites with nutraceutical and pharmaceutical benefits. The present review discusses biotechnological endeavors for producing bioprospective compounds from genetically engineered cyanobacteria and discusses the challenges and troubleshooting faced during metabolite production. This review explores the cyanobacterial versatility, the use of engineered strains, and the techno-economic challenges associated with scaling up metabolite production from cyanobacteria. Challenges to produce cyanobacterial bioactive compounds with remarkable nutraceutical values have been discussed. Additionally, this review also summarises the challenges and future prospects of metabolite production from genetically engineered cyanobacteria as a sustainable approach.

Substrate and functional characterization of the lysine acetyltransferase MsKat and deacetylase MsCobB in Mycobacterium smegmatis

Tuberculosis (TB) is a serious cause of infectious death worldwide. Recent studies have reported that about 30% of the Mtb proteome was modified post-translationally, indicating that their functions are essential for drug resistance, mycobacterial survival, and pathogenicity. Among them, lysine acetylation, reversibly regulated by acetyltransferase and deacetylase, has important roles involved in energy metabolism, cellular adaptation, and protein interactions. However, the substrate and biological functions of these two important regulatory enzymes remain unclear. Herein, we utilized the non-pathogenic M. smegmatis strain as a model and systematically investigated the dynamic proteome changes in response to the overexpressing of MsKat/MsCobB in mycobacteria. A total of 4179 proteins and 1236 acetylated sites were identified in our data. Further analysis of the dynamic changes involved in proteome and acetylome showed that MsKat/MsCobB played a regulatory role in various metabolic pathways and nucleic acid processes. After that, the quantitative mass spectrometric method was utilized and proved that the AMP-dependent synthetase, Citrate synthase, ATP-dependent specificity component of the Clp protease, and ATP-dependent DNA/RNA helicases were identified to be the substrates of MsKat. Overall, our study provided an important resource underlying the substrates and functions of the acetylation regulatory enzymes in mycobacteria. SIGNIFICANCE: In this study, we systematically analyzed the dynamic molecular changes in response to the MsKat/MsCobB overexpression in mycobacteria at proteome and lysine acetylation level by using a TMT-based quantitative proteomic approach. Pathways related with glycolysis, degradation of branched chain amino acids, phosphotransferase system were affected after disturbance of the two regulates enzymes involved in lysine acetylation. We also proved that AMP-dependent synthetase Clp protease, ATP-dependent DNA/RNA helicases and citrate synthase was the substrate of MsKat according to our proteomic data and biological validation. Together, our study underlined the substrates and functions of the acetylation regulatory enzymes in mycobacteria.

The Enzyme Lysine Malonylation of Calvin Cycle and Gluconeogenesis Regulated Glycometabolism in Nostoc flagelliforme to Adapt to Drought Stress

Lysine malonylation (Kmal) is an evolutionarily conserved post-translational modification (PTM) that has been demonstrated to be involved in cellular and organismal metabolism. However, the role that Kmal plays in response to drought stress of the terrestrial cyanobacteria N. flagelliforme is still unknown. In this study, we performed the first proteomic analysis of Kmal in N. flagelliforme under different drought stresses using LC-MS/MS. In total, 421 malonylated lysine residues were found in 236 different proteins. GO and KEGG enrichment analysis indicated that these malonylated proteins were highly enriched in several metabolic pathways, including carbon metabolism and photosynthesis. Decreased malonylation levels were found to hinder the reception and transmission of light energy and CO₂ fixation, which led to a decrease in photosynthetic activity. Kmal was also shown to inhibit the flux of the TCA cycle and activate the gluconeogenesis pathway in response to drought stress. Furthermore, malonylated antioxidant enzymes and antioxidants were synergistically involved in reactive oxygen species (ROS) scavenging. Malonylation was involved in lipid degradation and amino acid biosynthesis as part of drought stress adaptation. This work represents the first comprehensive investigation of the role of malonylation in dehydrated N. flagelliforme, providing an important resource for understanding the drought tolerance mechanism of this organism.

Lysine Malonylation and Its Links to Metabolism and Diseases

Malonylation is a recently identified post-translational modification with malonyl-coenzyme A as the donor. It conserved both in prokaryotes and eukaryotes. Recent advances in the identification and quantification of lysine malonylation by bioinformatic analysis have improved our understanding of its role in the regulation of protein activity, interaction, and localization and have elucidated its involvement in many biological processes. Malonylation has been linked to diverse physiological processes, including metabolic disorders, inflammation, and immune regulation. This review discusses malonylation in theory, describes the underlying mechanism, and summarizes the recent progress in malonylation research. The latest findings point to novel functions of malonylation and highlight the mechanisms by which malonylation regulates a variety of cellular processes. Our review also marks the association between lysine malonylation, the enzymes involved, and various diseases, and discusses promising diagnostic and therapeutic biomolecular targets for future clinical applications.

The increasing role of structural proteomics in cyanobacteria

Cyanobacteria, also known as blue–green algae, are ubiquitous organisms on the planet. They contain tremendous protein machineries that are of interest to the biotechnology industry and beyond. Recently, the number of annotated cyanobacterial genomes has expanded, enabling structural studies on known gene-coded proteins to accelerate. This review focuses on the advances in mass spectrometry (MS) that have enabled structural proteomics studies to be performed on the proteins and protein complexes within cyanobacteria. The review also showcases examples whereby MS has revealed critical mechanistic information behind how these remarkable machines within cyanobacteria function.

Malonylome analysis uncovers the association of lysine malonylation with metabolism and acidic stress in pathogenic Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb), the pathogenic agent of tuberculosis, remains a primary inducement of morbidity and mortality globally. Mtb have evolved mechanisms to recognize diverse signals, such as acidic pH within phagolysosomes and therefore to reprogram multiple physiological and metabolic processes to adapt to intracellular survival. Moreover, lysine malonylation has been suggested to participate in regulation of enzymes in carbon metabolism. However, lysine malonylation in Mtb and its association with acidic pH associated metabolism adaptation remain unknown. Here, we systematically characterized the comparative malonylome of Mtb H37Rv grown in normal (7H9-Tyloxapol (Ty)-7.4) and acidic (7H9-Ty-4.5) medium mimicking lysosome pH. In total, 2467 lysine malonylation sites within 1026 proteins were identified, which related to diverse biological processes, particularly accumulated in metabolic process. 1090 lysine malonylation sites from 562 proteins were quantified, among which 391 lysine malonylation sites in 273 protein were down-regulated while 40 lysine malonylation sites from 36 proteins were up-regulated in acidic medium, indicating that malonylation may participate in acidic pH associated metabolism. Accordingly, the enzyme activity of GlcB was reduced under acidic stress corresponding to decreased malonylation of GlcB compared with that of normal condition and this was further demonstrated by site-specific mutations. We further found that Mtb-CobB, a sirtuin-like deacetylase and desuccinylase, involved in demalonylase activity. Together, the Mtb malonylome not only indicates the critical role of malonylation in metabolism regulation, but may provide new insights of malonylation on metabolism adaptation to acidic micro-environment in vivo.

Metabolic systems biology and multi-omics of cyanobacteria: Perspectives and future directions

Cyanobacteria are oxygenic photoautotrophs whose metabolism contains key biochemical pathways to fix atmospheric CO₂ and synthesize various metabolites. The development of bioengineering tools has enabled the manipulation of cyanobacterial chassis to produce various valuable bioproducts photosynthetically. However, effective utilization of cyanobacteria as photosynthetic cell factories needs a detailed understanding of their metabolism and its interaction with other cellular processes. Implementing systems and synthetic biology tools has generated a wealth of information on various metabolic pathways. However, to design effective engineering strategies for further improvement in growth, photosynthetic efficiency, and enhanced production of target biochemicals, in-depth knowledge of their carbon/nitrogen metabolism, pathway fluxe distribution, genetic regulation and integrative analyses are necessary. In this review, we discuss the recent advances in the development of genome-scale metabolic models (GSMMs), omics analyses (metabolomics, transcriptomics, proteomics, fluxomics), and integrative modeling approaches to showcase the current understanding of cyanobacterial metabolism.

Systematic analysis of the lysine malonylome in Sanghuangporus sanghuang

Background

Sanghuangporus sanghuang is a well-known traditional medicinal mushroom associated with mulberry. Despite the properties of this mushroom being known for many years, the regulatory mechanisms of bioactive compound biosynthesis in this medicinal mushroom are still unclear. Lysine malonylation is a posttranslational modification that has many critical functions in various aspects of cell metabolism. However, at present we do not know its role in S. sanghuang. In this study, a global investigation of the lysine malonylome in S. sanghuang was therefore carried out.

Results

In total, 714 malonyl modification sites were matched to 255 different proteins. The analysis indicated that malonyl modifications were involved in a wide range of cellular functions and displayed a distinct subcellular localization. Bioinformatics analysis indicated that malonylated proteins were engaged in different metabolic pathways, including glyoxylate and dicarboxylate metabolism, glycolysis/gluconeogenesis, and the tricarboxylic acid (TCA) cycle. Notably, a total of 26 enzymes related to triterpene and polysaccharide biosynthesis were found to be malonylated, indicating an indispensable role of lysine malonylation in bioactive compound biosynthesis in S. sanghuang.

Conclusions

These findings suggest that malonylation is associated with many metabolic pathways, particularly the metabolism of the bioactive compounds triterpene and polysaccharide. This paper represents the first comprehensive survey of malonylation in S. sanghuang and provides important data for further study on the physiological function of lysine malonylation in S. sanghuang and other medicinal mushrooms.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08120-0.

CyanoOmicsDB: an integrated omics database for functional genomic analysis of cyanobacteria

With their photosynthetic ability and established genetic modification systems, cyanobacteria are essential for fundamental and biotechnological research. Till now, hundreds of cyanobacterial genomes have been sequenced, and transcriptomic analysis has been frequently applied in the functional genomics of cyanobacteria. However, the massive omics data have not been extensively mined and integrated. Here, we describe CyanoOmicsDB (http://www.cyanoomics.cn/), a database aiming to provide comprehensive functional information for each cyanobacterial gene. CyanoOmicsDB consists of 8 335 261 entries of cyanobacterial genes from 928 genomes. It provides multiple gene identifiers, visualized genomic location, and DNA sequences for each gene entry. For protein-encoding genes, CyanoOmicsDB can provide predicted gene function, amino acid sequences, homologs, protein-domain super-families, and accession numbers for various public protein function databases. CyanoOmicsDB integrates both transcriptional and translational profiles of Synechocystis sp. PCC 6803 under various environmental culture coditions and genetic backgrounds. Moreover, CyanoOmicsDB includes 23 689 gene transcriptional start sites, 94 644 identified peptides, and 16 778 post-translation modification sites obtained from transcriptomes or proteomes of several model cyanobacteria. Compared with other existing cyanobacterial databases, CyanoOmicsDB comprises more datasets and more comprehensive functional information. CyanoOmicsDB will provide researchers in this field with a convenient way to retrieve functional information on cyanobacterial genes.

Global Identification and Systematic Analysis of Lysine Malonylation in Maize (Zea mays L.)

Lysine malonylation is a kind of post-translational modifications (PTMs) discovered in recent years, which plays an important regulatory role in plants. Maize (Zea mays L.) is a major global cereal crop. Immunoblotting revealed that maize was rich in malonylated proteins. We therefore performed a qualitative malonylome analysis to globally identify malonylated proteins in maize. In total, 1,722 uniquely malonylated lysine residues were obtained in 810 proteins. The modified proteins were involved in various biological processes such as photosynthesis, ribosome and oxidative phosphorylation. Notably, a large proportion of the modified proteins (45%) were located in chloroplast. Further functional analysis revealed that 30 proteins in photosynthesis and 15 key enzymes in the Calvin cycle were malonylated, suggesting an indispensable regulatory role of malonylation in photosynthesis and carbon fixation. This work represents the first comprehensive survey of malonylome in maize and provides an important resource for exploring the function of lysine malonylation in physiological regulation of maize.

Genetic, Genomics, and Responses to Stresses in Cyanobacteria: Biotechnological Implications

Cyanobacteria are widely-diverse, environmentally crucial photosynthetic prokaryotes of great interests for basic and applied science. Work to date has focused mostly on the three non-nitrogen fixing unicellular species Synechocystis PCC 6803, Synechococcus PCC 7942, and Synechococcus PCC 7002, which have been selected for their genetic and physiological interests summarized in this review. Extensive "omics" data sets have been generated, and genome-scale models (GSM) have been developed for the rational engineering of these cyanobacteria for biotechnological purposes. We presently discuss what should be done to improve our understanding of the genotype-phenotype relationships of these models and generate robust and predictive models of their metabolism. Furthermore, we also emphasize that because Synechocystis PCC 6803, Synechococcus PCC 7942, and Synechococcus PCC 7002 represent only a limited part of the wide biodiversity of cyanobacteria, other species distantly related to these three models, should be studied. Finally, we highlight the need to strengthen the communication between academic researchers, who know well cyanobacteria and can engineer them for biotechnological purposes, but have a limited access to large photobioreactors, and industrial partners who attempt to use natural or engineered cyanobacteria to produce interesting chemicals at reasonable costs, but may lack knowledge on cyanobacterial physiology and metabolism.

Characterization of Lysine Monomethylome and Methyltransferase in Model Cyanobacterium Synechocystis sp. PCC 6803

Protein lysine methylation is a prevalent post-translational modification (PTM) and plays critical roles in all domains of life. However, its extent and function in photosynthetic organisms are still largely unknown. Cyanobacteria are a large group of prokaryotes that carry out oxygenic photosynthesis and are applied extensively in studies of photosynthetic mechanisms and environmental adaptation. Here we integrated propionylation of monomethylated proteins, enrichment of the modified peptides, and mass spectrometry (MS) analysis to identify monomethylated proteins in Synechocystis sp. PCC 6803 (Synechocystis). Overall, we identified 376 monomethylation sites in 270 proteins, with numerous monomethylated proteins participating in photosynthesis and carbon metabolism. We subsequently demonstrated that CpcM, a previously identified asparagine methyltransferase in Synechocystis, could catalyze lysine monomethylation of the potential aspartate aminotransferase Sll0480 both in vivo and in vitro and regulate the enzyme activity of Sll0480. The loss of CpcM led to decreases in the maximum quantum yield in primary photosystem II (PSII) and the efficiency of energy transfer during the photosynthetic reaction in Synechocystis. We report the first lysine monomethylome in a photosynthetic organism and present a critical database for functional analyses of monomethylation in cyanobacteria. The large number of monomethylated proteins and the identification of CpcM as the lysine methyltransferase in cyanobacteria suggest that reversible methylation may influence the metabolic process and photosynthesis in both cyanobacteria and plants.

Global Proteomic Analysis of Lysine Malonylation in Toxoplasma gondii

Lysine malonylation (Kmal) is a new post-translational modification (PTM), which has been reported in several prokaryotic and eukaryotic species. Although Kmal can regulate many and diverse biological processes in various organisms, knowledge about this important PTM in the apicomplexan parasite Toxoplasma gondii is limited. In this study, we performed the first global profiling of malonylated proteins in T. gondii tachyzoites using affinity enrichment and Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Three experiments performed in tandem revealed 294, 345, 352 Kmal sites on 203, 236, 230 malonylated proteins, respectively. Computational analysis showed the identified malonylated proteins to be localized in various subcellular compartments and involved in many cellular functions, particularly mitochondrial function. Additionally, one conserved Kmal motif with a strong bias for cysteine was detected. Taken together, these findings provide the first report of Kmal profile in T. gondii and should be an important resource for studying the physiological roles of Kmal in this parasite.

Protein lysine de-2-hydroxyisobutyrylation by CobB in prokaryotes

Lysine 2-hydroxyisobutyrylation (Khib) has recently been shown to be an evolutionarily conserved histone mark. Here, we report that CobB serves as a lysine de-2-hydroxyisobutyrylation enzyme that regulates glycolysis and cell growth in prokaryotes. We identified the specific binding of CobB to Khib using a novel self-assembled multivalent photocrosslinking peptide probe and demonstrated that CobB can catalyze lysine de-2-hydroxyisobutyrylation both in vivo and in vitro. R58 of CobB is a critical site for its de-2-hydroxyisobutyrylase activity. Using a quantitative proteomics approach, we identified 99 endogenous substrates that are targeted by CobB for de-2-hydroxyisobutyrylation. We further demonstrated that CobB can regulate the catalytic activities of enolase (ENO) by removing K343hib and K326ac of ENO simultaneously, which account for changes of bacterial growth. In brief, our study dissects a Khib-mediated molecular mechanism that is catalyzed by CobB for the regulation of the activity of metabolic enzymes as well as the cell growth of bacteria.

Proteomic De-Regulation in Cyanobacteria in Response to Abiotic Stresses

Cyanobacteria are oxygenic photoautotrophs, exhibiting a cosmopolitan distribution in almost all possible environments and are significantly responsible for half of the global net primary productivity. They are well adapted to the diverse environments including harsh conditions by evolving a range of fascinating repertoires of unique biomolecules and secondary metabolites to support their growth and survival. These phototrophs are proved as excellent models for unraveling the mysteries of basic biochemical and physiological processes taking place in higher plants. Several known species of cyanobacteria have tremendous biotechnological applications in diverse fields such as biofuels, biopolymers, secondary metabolites and much more. Due to their potential biotechnological and commercial applications in various fields, there is an imperative need to engineer robust cyanobacteria in such a way that they can tolerate and acclimatize to ever-changing environmental conditions. Adaptations to stress are mainly governed by a precise gene regulation pathways resulting in the expression of novel protein/enzymes and metabolites. Despite the demand, till date few proteins/enzymes have been identified which play a potential role in improving tolerance against abiotic stresses. Therefore, it is utmost important to study environmental stress responses related to post-genomic investigations, including proteomic changes employing advanced proteomics, synthetic and structural biology workflows. In this respect, the study of stress proteomics offers exclusive advantages to scientists working on these aspects. Advancements on these fields could be helpful in dissecting, characterization and manipulation of physiological and metabolic systems of cyanobacteria to understand the stress induced proteomic responses. Till date, it remains ambiguous how cyanobacteria perceive changes in the ambient environment that lead to the stress-induced proteins thus metabolic deregulation. This review briefly describes the current major findings in the fields of proteome research on the cyanobacteria under various abiotic stresses. These findings may improve and advance the information on the role of different class of proteins associated with the mechanism(s) of stress mitigation in cyanobacteria under harsh environmental conditions.

LasB and CbpD Virulence Factors of Pseudomonas aeruginosa Carry Multiple Post-Translational Modifications on Their Lysine Residues

Pseudomonas aeruginosa is a multi-drug resistant human pathogen largely involved in nosocomial infections. Today, effective antibacterial agents are lacking. Exploring the bacterial physiology at the post-translational modifications (PTM) level may contribute to the renewal of fighting strategies. Indeed, some correlations between PTMs and the bacterial virulence, adaptation, and resistance have been shown. In a previous study performed in P. aeruginosa, we reported that many virulence factors like chitin-binding protein CbpD and elastase LasB were multiphosphorylated. Besides phosphorylation, other PTMs, like those occurring on lysine, seem to play key roles in bacteria. In the present study, we investigated for the first time the lysine succinylome and acetylome of the extracellular compartment of P. aeruginosa by using a two-dimensional immunoaffinity approach. Some virulence factors were identified as multimodified on lysine residues, among them, LasB and CbpD. Lysine can be modified by a wide range of chemical groups. In order to check the presence of other chemical groups on modified lysines identified on LasB and CbpD, we used 1- and 2- dimensional gel electrophoresis approaches to target lysine modified by 7 other modifications: butyrylation, crotonylation, dimethylation, malonylation, methylation, propionylation, and trimethylation. We showed that some lysines of these two virulence factors were modified by these 9 different PTMs. Interestingly, we found that the PTMs recovered on these two virulence factors were different than those previously reported in the intracellular compartment.

Computational Method for Identifying Malonylation Sites by Using Random Forest Algorithm

BACKGROUND

As a newly uncovered post-translational modification on the ε-amino group of lysine residue, protein malonylation was found to be involved in metabolic pathways and certain diseases. Apart from experimental approaches, several computational methods based on machine learning algorithms were recently proposed to predict malonylation sites. However, previous methods failed to address imbalanced data sizes between positive and negative samples.

OBJECTIVE

In this study, we identified the significant features of malonylation sites in a novel computational method which applied machine learning algorithms and balanced data sizes by applying synthetic minority over-sampling technique.

METHOD

Four types of features, namely, amino acid (AA) composition, position-specific scoring matrix (PSSM), AA factor, and disorder were used to encode residues in protein segments. Then, a two-step feature selection procedure including maximum relevance minimum redundancy and incremental feature selection, together with random forest algorithm, was performed on the constructed hybrid feature vector.

RESULTS

An optimal classifier was built from the optimal feature subset, which featured an F1-measure of 0.356. Feature analysis was performed on several selected important features.

CONCLUSION

Results showed that certain types of PSSM and disorder features may be closely associated with malonylation of lysine residues. Our study contributes to the development of computational approaches for predicting malonyllysine and provides insights into molecular mechanism of malonylation.

Protein Acylation Affects the Artificial Biosynthetic Pathway for Pinosylvin Production in Engineered E. coli

The effect of regulatory system on the engineered biosynthetic pathway in chassis cells remains incompletely understood in microorganisms. Acyl-CoAs function as key precursors for the biosynthesis of various natural products and the dominant donors for protein acylation. The polyphenol pinosylvin, with high antimicrobial and antifungal activities, is biosynthesized with malonyl-CoA as its direct precursors. But correlation between lysine malonylation and pinosylvin biosynthesis remains unknown. Herein, we found that the malonyl-CoA-driven lysine malonylation plays an important role in interaction between the engineered pathway of pinosylvin synthesis and E. coli chassis cell. Oversupply of malonyl-CoA leads to an increase in malonylation level of global proteome as well as the enzymes in the artificial pathway, thereby decreasing yield of pinosylvin. The results revealed that the intricate balance of cellular acyl-CoA concentrations is critical for the yields of acyl-CoA-derived natural products. We next modified the enzymes in the biosynthetic pathway to adjust their acylation level and successfully improved the yield of pinosylvin. Our study uncovers the effect of protein acylation on the biosynthetic pathway, helps optimization of synthetic constructs, and provides new strategies in metabolic engineering and synthetic biology at the protein post-translational level.

Systematic analysis of the lysine malonylome in common wheat

Background

Protein lysine malonylation, a newly discovered post-translational modification (PTM), plays an important role in diverse metabolic processes in both eukaryotes and prokaryotes. Common wheat is a major global cereal crop. However, the functions of lysine malonylation are relatively unknown in this crop. Here, a global analysis of lysine malonylation was performed in wheat.

Results

In total, 342 lysine malonylated sites were identified in 233 proteins. Bioinformatics analysis showed that the frequency of arginine (R) in position + 1 was highest, and a modification motif, K^maR, was identified. The malonylated proteins were located in multiple subcellular compartments, especially in the cytosol (45%) and chloroplast (30%). The identified proteins were found to be involved in diverse pathways, such as carbon metabolism, the Calvin cycle, and the biosynthesis of amino acids, suggesting an important role for lysine malonylation in these processes. Protein interaction network analysis revealed eight highly interconnected clusters of malonylated proteins, and 137 malonylated proteins were mapped to the protein network database. Moreover, five proteins were simultaneously modified by lysine malonylation, acetylation and succinylation, suggesting that these three PTMs may coordinately regulate the function of many proteins in common wheat.

Conclusions

Our results suggest that lysine malonylation is involved in a variety of biological processes, especially carbon fixation in photosynthetic organisms. These data represent the first report of the lysine malonylome in common wheat and provide an important dataset for further exploring the physiological role of lysine malonylation in wheat and likely all plants.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4535-y) contains supplementary material, which is available to authorized users.

Protein Acetylation and Butyrylation Regulate the Phenotype and Metabolic Shifts of the Endospore-forming Clostridium acetobutylicum

Clostridium acetobutylicum is a strict anaerobic, endospore-forming bacterium, which is used for the production of the high energy biofuel butanol in metabolic engineering. The life cycle of C. acetobutylicum can be divided into two phases, with acetic and butyric acids being produced in the exponential phase (acidogenesis) and butanol formed in the stationary phase (solventogenesis). During the transitional phase from acidogenesis to solventogenesis and latter stationary phase, concentration peaks of the metabolic intermediates butyryl phosphate and acetyl phosphate are observed. As an acyl group donor, acyl-phosphate chemically acylates protein substrates. However, the regulatory mechanism of lysine acetylation and butyrylation involved in the phenotype and solventogenesis of C. acetobutylicum remains unknown. In our study, we conducted quantitative analysis of protein acetylome and butyrylome to explore the dynamic change of lysine acetylation and butyrylation in the exponential phase, transitional phase, and stationary phase of C. acetobutylicum Total 458 lysine acetylation sites and 1078 lysine butyrylation sites were identified in 254 and 373 substrates, respectively. Bioinformatics analysis uncovered the similarities and differences between the two acylation modifications in C. acetobutylicum Mutation analysis of butyrate kinase and the central transcriptional factor Spo0A was performed to characterize the unique role of lysine butyrylation in the metabolic pathway and sporulation process of C. acetobutylicum Moreover, quantitative proteomic assays were performed to reveal the relationship between protein features (e.g. gene expression level and lysine acylation level) and metabolites in the three growth stages. This study expanded our knowledge of lysine acetylation and butyrylation in Clostridia and constituted a resource for functional studies on lysine acylation in bacteria.

Malonylome analysis in developing rice (Oryza sativa) seeds suggesting that protein lysine malonylation is well-conserved and overlaps with acetylation and succinylation substantially

In recent years, lysine malonylation has garnered wide spread interest due to its potential regulatory roles. While studies have been performed in bacteria, mouse, and human, the involvement and the biological function of this modification in plant are still largely unknown. We examined the global proteome profile of lysine malonylation in developing rice seeds using affinity enrichment followed by LC-MS/MS analysis. We identified 421 malonylated lysine sites across 247 proteins. Functional analyses showed predominant presence of malonylated proteins in metabolic processes, including carbon metabolism, glycolysis/gluconeogenesis, TCA cycle, as well as photosynthesis. Malonylation was also detected on enzymes in starch biosynthesis pathway in developing rice seeds. In addition, we found a remarkable overlap among the malonylated, succinylated and acetylated sites identified in rice. Furthermore, malonylation at conserved sites of homologous proteins was observed across organisms of different kingdoms, including mouse, human, and bacteria. Finally, distinct motifs were identified when the rice malonylation sites were analyzed and conserved motifs were observed from bacterium to human and rice. Our results provide an initial understanding of the lysine malonylome in plants. The study has critical reference value for future understanding of the biological function of protein lysine malonylation in plants.

BIOLOGICAL SIGNIFICANCE

Lysine malonylation is a newly discovered acylation with functional potential in regulating cellular metabolisms and activities. However, the malonylation status has not been reported in plants. Grain yield and quality, mainly determined during cereal seed development, are closely related to food security, human health and economic value. To evaluate malonylation level in plants and the possible regulatory functions of malonylation in seed development, we conducted comprehensive analyses of malonylome in developing rice seeds. A total of 421 malonylated lysine sites from 247 proteins were identified, which involved in multiple critical metabolic processes, including central carbon metabolism, lipid metabolism, photosynthesis, and starch biosynthesis. We found that charged amino acids, lysine and arginine, were the preferred residues in positions flanking the modified lysines. Highly conserved modification sites on both histone and non-histone proteins were observed among different organisms through sequence alignment analysis. More interestingly, a large number of modification sites shared by malonylation, acetylation and succinylation were identified in rice. The study presents a comprehensive understanding of malonylome in plants, which will serve as an initial platform for further investigation of the functions of lysine malonylation, especially in cereal seeds development.