首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 187 毫秒
1.
Myristoyl-CoA:protein N-myristoyl transferase (NMT; EC 2.3.1.97) acylates the Gly residue abutting the N-terminal Met with a myristic acid following the removal of the Met residue in certain eukaryotic proteins, and in some cases myristoylation is essential to cell growth and survival. We report the cloning of a full-length cDNA encoding NMT from Triticum aestivum (TaNMT). The cDNA included a predicted open reading frame of 1317 nucleotides, which encoded a predicted protein of 438 amino acids containing all of the residues that are important for NMT activity. The TaNMT amino acid and nucleotide sequences were compared with NMTs from 14 other species encompassing a wide array of taxonomic groups. Among the experimentally validated NMTs, TaNMT was most similar to that of Arabidopsis thaliana. Southern blot analysis of wheat genomic DNA showed that TaNMT is encoded by a single copy gene, with one copy per haploid genome. We expressed TaNMT in Escherichia coli cells and determined that the recombinant protein possessed NMT activity, catalyzing the N-myristoylation of peptides from known or putatively myristoylated proteins from plants and animals without a strong preference for the plant peptides. TaNMT is the second experimentally validated plant NMT sequence and the first from a monocotyledonous species.  相似文献   

2.
Myristoylation is a lipid modification involving the addition of a 14-carbon unsaturated fatty acid, myristic acid, to the N-terminal glycine of a subset of proteins, a modification that promotes their binding to cell membranes for varied biological functions. The process is catalyzed by myristoyl-CoA:protein N-myristoyltransferase (NMT), an enzyme which has been validated as a drug target in human cancers, and for infectious diseases caused by fungi, viruses and protozoan parasites. We purified Caenorhabditis elegans and Brugia malayi NMTs as active recombinant proteins and carried out kinetic analyses with their essential fatty acid donor, myristoyl-CoA and peptide substrates. Biochemical and structural analyses both revealed that the nematode enzymes are canonical NMTs, sharing a high degree of conservation with protozoan NMT enzymes. Inhibitory compounds that target NMT in protozoan species inhibited the nematode NMTs with IC50 values of 2.5–10 nM, and were active against B. malayi microfilariae and adult worms at 12.5 µM and 50 µM respectively, and C. elegans (25 µM) in culture. RNA interference and gene deletion in C. elegans further showed that NMT is essential for nematode viability. The effects observed are likely due to disruption of the function of several downstream target proteins. Potential substrates of NMT in B. malayi are predicted using bioinformatic analysis. Our genetic and chemical studies highlight the importance of myristoylation in the synthesis of functional proteins in nematodes and have shown for the first time that NMT is required for viability in parasitic nematodes. These results suggest that targeting NMT could be a valid approach for the development of chemotherapeutic agents against nematode diseases including filariasis.  相似文献   

3.
N-myristoylation is the irreversible attachment of a C(14) fatty acid, myristic acid, to the N-terminal glycine of a protein via formation of an amide bond. This modification is catalyzed by myristoyl-coenzyme A (CoA):protein N-myristoyltransferase (NMT), an enzyme ubiquitous in eukaryotes that is up-regulated in several cancers. Here we report a sensitive fluorescence-based assay to study the enzymatic activity of human NMT1 and NMT2 based on detection of CoA by 7-diethylamino-3-(4-maleimido-phenyl)-4-methylcoumarin. We also describe expression and characterization of NMT1 and NMT2 and assay validation with small molecule inhibitors. This assay should be broadly applicable to NMTs from a range of organisms.  相似文献   

4.
Nef is a multifunctional virulence factor of primate lentiviruses that facilitates viral replication in the infected host. All known functions of Nef require that it be myristoylated at its N terminus. This reaction is catalyzed by N-myristoyltransferases (NMTs), which transfer myristate from myristoyl coenzyme A (myristoyl-CoA) to the N-terminal glycine of substrate proteins. Two NMT isoforms (NMT-1 and NMT-2) are expressed in mammalian cells. To provide a better mechanistic understanding of Nef function, we used biochemical and microsequencing techniques to isolate and identify Nef-associated proteins. Through these studies, NMT-1 was identified as an abundant Nef-associated protein. The Nef-NMT-1 complex is most likely a transient intermediate of the myristoylation reaction of Nef and is modulated by agents which affect the size of the myristoyl-CoA pool in the cell. We also examined two other proteins that bear an N-terminal myristoylation signal, human immunodeficiency virus type 1 Gag and Hck protein tyrosine kinase, and found that Gag bound preferentially the NMT-2 isoform, while Hck bound mostly to NMT-1. Recognition of different NMT isoforms by these viral and cellular substrate proteins suggests nonoverlapping roles for these enzymes in vivo and reveals a potential for the development of inhibitors that target the myristoylation of specific viral substrates more selectively.  相似文献   

5.
Myristoyl-CoA (CoA):protein N-myristoyltransferase (NMT) catalyzes protein modification through covalent attachment of a C14 fatty acid (myristic acid) to the N-terminal glycine of proteins, thus promoting protein-protein and protein-membrane interactions. NMT is essential for the viability of numerous human pathogens and is also up-regulated in several tumors. Here we describe a new, nonradioactive, ELISA-based method for measuring NMT activity. After the NMT-catalyzed reaction between a FLAG-tagged peptide and azido-dodecanoyl-CoA (analog of myristoyl-CoA), the resulting azido-dodecanoyl-peptide-FLAG was coupled to phosphine-biotin by Staudinger ligation, captured by plate-bound anti-FLAG antibodies and detected by streptavidin-peroxidase. The assay was validated with negative controls (including inhibitors), corroborated by HPLC analysis, and demonstrated to function with fresh or frozen tissues. Recombinant murine NMT1 and NMT2 were characterized using this new method. This versatile assay is applicable for exploring recombinant NMTs with regard to their activity, substrate specificity, and possible inhibitors as well as for measuring NMT-activity in tissues.  相似文献   

6.
N-terminal N-myristoylation is a lipid anchor modification of eukaryotic and viral proteins targeting them to membrane locations, thus changing the cellular function of modified proteins. Protein myristoylation is critical in many pathways; e.g. in signal transduction, apoptosis, or alternative extracellular protein export. The myristoyl-CoA:protein N-myristoyltransferase (NMT) recognizes the sequence motif of appropriate substrate proteins at the N terminus and attaches the lipid moiety to the absolutely required N-terminal glycine residue. Reliable recognition of capacity for N-terminal myristoylation from the substrate protein sequence alone is desirable for proteome-wide function annotation projects but the existing PROSITE motif is not practical, since it produces huge numbers of false positive and even some false negative predictions.As a first step towards a new prediction method, it is necessary to refine the sequence motif coding for N-terminal N-myristoylation. Relying on the in-depth study of the amino acid sequence variability of substrate proteins, on binding site analyses in X-ray structures or 3D homology models for NMTs from various taxa, and on consideration of biochemical data extracted from the scientific literature, we found indications that, at least within a complete substrate protein, the N-terminal 17 protein residues experience different types of variability restrictions. We identified three motif regions: region 1 (positions 1-6) fitting the binding pocket; region 2 (positions 7-10) interacting with the NMT's surface at the mouth of the catalytic cavity; and region 3 (positions 11-17) comprising a hydrophilic linker. Each region was characterized by physical requirements to single sequence positions or groups of positions regarding volume, polarity, backbone flexibility and other typical properties of amino acids (http://mendel.imp.univie.ac.at/myristate/). These specificity differences are confined partly to taxonomic ranges and are proposed for the design of NMT inhibitors in pathogenic fungal and protozoan systems including Aspergillus fumigatus, Leishmania major, Trypanosoma cruzi, Trypanosoma brucei, Giardia intestinalis, Entamoeba histolytica, Pneumocystis carinii, Strongyloides stercoralis and Schistosoma mansoni. An exhaustive search for NMT-homologues led to the discovery of two putative entomopoxviral NMTs.  相似文献   

7.
Dihydroceramide Delta4-desaturase (DES) catalyzes the desaturation of dihydroceramide into ceramide. In mammals, two gene isoforms named DES1 and DES2 have recently been identified. The regulation of these enzymes is still poorly understood. This study was designed to examine the possible N-myristoylation of DES1 and DES2 and the effect of this co-translational modification on dihydroceramide Delta4-desaturase activity. N-MyristoylTransferases (NMT) catalyze indeed the formation of a covalent linkage between myristoyl-CoA and the N-terminal glycine of candidate proteins, as found in the sequence of DES proteins. The expression of both rat DES in COS-7 cells evidenced first that DES1 but not DES2 was associated with an increased dihydroceramide Delta4-desaturase activity. Then, we showed that recombinant DES1 was myristoylated in vivo when expressed in COS-7 cells. In addition, in vitro myristoylation assay with a peptide substrate corresponding to the N-terminal sequence of the protein confirmed that NMT1 has a high affinity for DES1 myristoylation motif (apparent K(m)=3.92 microM). Compared to an unmyristoylable mutant form of DES1 (Gly replaced by an Ala), the dihydroceramide Delta4-desaturase activity of the myristoylable DES1-Gly was reproducibly and significantly higher. Finally, the activity of wild-type DES1 was also linearly increased in the presence of increased concentrations of myristic acid incubated with the cells. These results demonstrate that DES1 is a newly discovered myristoylated protein. This N-terminal modification has a great impact on dihydroceramide Delta4-desaturase activity. These results suggest therefore that myristic acid may play an important role in the biosynthesis of ceramide and in sphingolipid metabolism.  相似文献   

8.
N-myristoylation is the attachment of a 14-carbon fatty acid, myristate, onto the N-terminal glycine residue of target proteins, catalysed by N-myristoyltransferase (NMT), a ubiquitous and essential enzyme in eukaryotes. Many of the target proteins of NMT are crucial components of signalling pathways, and myristoylation typically promotes membrane binding that is essential for proper protein localisation or biological function. NMT is a validated therapeutic target in opportunistic infections of humans by fungi or parasitic protozoa. Additionally, NMT is implicated in carcinogenesis, particularly colon cancer, where there is evidence for its upregulation in the early stages of tumour formation. However, the study of myristoylation in all organisms has until recently been hindered by a lack of techniques for detection and identification of myristoylated proteins. Here we introduce the chemistry and biology of N-myristoylation and NMT, and discuss new developments in chemical proteomic technologies that are meeting the challenge of studying this important co-translational modification in living systems.  相似文献   

9.
The importance of myristoylation for the proper biological functioning of many acylated proteins has generated interest in the enzymes of the myristoylation pathway and their interactions with substrates and inhibitors. Previous observations that S-(2-oxopentadecyl)-CoA, a nonhydrolyzable methylene-bridged analogue of myristoyl-CoA, was a potent inhibitor of myristoyl-CoA:protein N-myristoyltransferase (NMT) [Paige, L. A., Zheng, G.-q., DeFrees, S. A., Cassady, J. M., & Geahlen, R. L. (1989) J. Med. Chem. 32, 1665] prompted a closer examination of the effect of substituents at the 2-position on the interactions of myristic acid and myristoyl-CoA analogues with NMT. As an initial approach, three myristic acid derivatives bearing different substituents at the 2-position, 2-fluoromyristic acid, 2-bromomyristic acid, and 2-hydroxymyristic acid, were selected for study. Both 2-bromomyristic acid and 2-hydroxymyristic acid were available commercially; 2-fluoromyristic acid was prepared synthetically. All three compounds were found to be only weak inhibitors of NMT in vitro. Of the three, 2-bromomyristic acid was the most potent (Ki = 100 microM). In cultured cells, however, 2-hydroxymyristic acid was by far the more effective inhibitor of protein myristoylation. Neither 2-hydroxymyristic acid nor 2-bromomyristic acid significantly inhibited protein palmitoylation in cultured cells, indicating that inhibition was not occurring at the level of acyl-CoA synthetase. Activation of the 2-substituted myristic acid derivatives to their corresponding acyl-CoA thioesters by acyl-CoA synthetase resulted in inhibitors of greatly increased potency. The 2-substituted acyl-CoA analogues, 2-hydroxymyristoyl-CoA, 2-bromomyristoyl-CoA, and 2-fluoromyristoyl-CoA, were synthesized and shown to be competitive inhibitors of NMT in vitro (Ki's = 45, 450, and 200 nM, respectively). These data suggested that the enhanced inhibitory potency of 2-hydroxymyristic acid seen in cells was most probably a result of its metabolic activation to the CoA thioester. The presence of substituents at the 2-position also affected the ability of the acyl group to be transferred by NMT to a peptide substrate. Of the three acyl-CoA analogues, only 2-fluoromyristoyl-CoA served as a substrate for NMT.  相似文献   

10.
The effects of two myristic acid analogs on Junin virus (JV) replication were investigated. The compounds chosen for the study were DL-2-hydroxymyristic acid (2OHM), an inhibitor of N-myristoyltransferase (NMT), which binds the enzyme and blocks protein myristoylation, and 13-oxamyristic acid (13OM), a competitive inhibitor of NMT which incorporates into the protein instead of myristic acid. Both types of analogs achieved dose-dependent inhibition of viral multiplication at concentrations not affecting cell viability. The 50% inhibitory concentration values determined by a virus-yield inhibition assay for different strains of JV, including a human pathogenic strain, and for the related arenavirus, Tacaribe, were in the range 1.6 to 20.1 microM, with 13OM as the most active compound. From time of addition and removal experiments, it can be concluded that both analogs inhibit a late stage in the JV replicative cycle, and their effect was partially reversible. The cytoplasmic and surface expression of JV glycoproteins was not affected in the presence of the compounds, as revealed by immunofluorescence staining, suggesting that JV glycoprotein myristoylation would not be essential for the intracellular transport of the envelope proteins, but it may have an important role in their interaction with the plasma membrane during virus budding.  相似文献   

11.
The arenavirus small RING finger Z protein is the main driving force of arenavirus budding. The primary structure of Z is devoid of hydrophobic transmembrane domains, but both lymphocytic choriomeningitis virus (LCMV) and Lassa fever virus Z proteins accumulate near the inner surface of the plasma membrane and are strongly membrane associated. All known arenavirus Z proteins contain a glycine (G) at position 2, which is a potential acceptor site for a myristoyl moiety. Metabolic labeling showed incorporation of [(3)H]myristic acid by wild-type Z protein but not by the G2A mutant. The mutation G2A eliminated Z-mediated budding. Likewise, treatment with the myristoylation inhibitor 2-hydroxymyristic acid inhibited Z-mediated budding, eliminated formation of virus-like particles, and caused a dramatic reduction in virus production in LCMV-infected cells. Budding activity was restored in G2A mutant Z proteins by the addition of the myristoylation domain of the tyrosine protein kinase Src to their N termini. These findings indicate N-terminal myristoylation of Z plays a key role in arenavirus budding.  相似文献   

12.
Proteins with N-terminal cysteine can undergo native chemical ligation and are useful for site-specific N-terminal labeling or protein semisynthesis. Recombinant production of these has usually been by site-specific cleavage of a precursor fusion protein at an internal cysteine residue. Here we describe a simpler route to producing these proteins. Overexpression in E. coli of several proteins containing cysteine as the second amino acid residue yielded products in which the initiating methionine residue had been completely cleaved by endogenous methionine aminopeptidase. While secondary modification of the terminal cysteine was a complicating factor, conditions were identified to eliminate or minimize this problem. Recombinant proteins produced in this way were suitable for site-specific modification of the amino terminus via native chemical ligation technology, as demonstrated by conjugation of a thioester-containing derivative of fluorescein to one such protein. The ability to directly produce proteins with N-terminal cysteine should simplify the application of native chemical ligation technology to recombinant proteins and make the technique more amenable to researchers with limited expertise in protein chemistry.  相似文献   

13.
N-myristoyltransferases (NMTs) catalyze protein myristoylation, a lipid modification crucial for cell survival and a range of pathophysiological processes. Originally thought to modify only N-terminal glycine α-amino groups (G-myristoylation), NMTs were recently shown to also modify lysine ε-amino groups (K-myristoylation). However, the clues ruling NMT-dependent K-myristoylation and the full range of targets are currently unknown. Here we combine mass spectrometry, kinetic studies, in silico analysis, and crystallography to identify the specific features driving each modification. We show that direct interactions between the substrate’s reactive amino group and the NMT catalytic base promote K-myristoylation but with poor efficiency compared to G-myristoylation, which instead uses a water-mediated interaction. We provide evidence of depletion of proteins with NMT-dependent K-myristoylation motifs in humans, suggesting evolutionary pressure to prevent this modification in favor of G-myristoylation. In turn, we reveal that K-myristoylation may only result from post-translational events. Our studies finally unravel the respective paths towards K-myristoylation or G-myristoylation, which rely on a very subtle tradeoff embracing the chemical landscape around the reactive group.  相似文献   

14.
Myristoylation (MYR) is a protein modification where a myristoyl group is covalently attached to an exposed (N-terminal) glycine residue. Glycine myristoylation occurs during protein translation (co-translation) or after (post-translation). Myristoylated proteins have a role in signal transduction, apoptosis, and pathogen-mediated processes and their prediction can help in functionally annotating the fraction of proteins undergoing MYR in different proteomes.Here we present SVMyr, a web server allowing the detection of both co- and post-translational myristoylation sites, based on Support Vector Machines (SVM). The input encodes composition and physicochemical features of the octapeptides, known to act as substrates and to physically interact with N-myristoyltransferases (NMTs), the enzymes catalyzing the myristoylation reaction.The method, adopting a cross validation procedure, scores with values of Area Under the Curve (AUC) and Matthews Correlation Coefficient (MCC) of 0.92 and 0.61, respectively. When benchmarked on an independent dataset including experimentally detected 88 medium/high confidence co-translational myristoylation sites and 528 negative examples, SVMyr outperforms available methods, with AUC and MCC equal to 0.91 and 0.58, respectively.A unique feature of SVMyr is the ability to predict post-translational myristoylation sites by coupling the trained SVMs with the detection of caspase cleavage sites, identified by searching regular motifs matching upstream caspase cleavage sites, as reported in literature.Finally, SVMyr confirms 96% of the UniProt set of the electronically annotated myristoylated proteins (31,048) and identifies putative myristoylomes in eight different proteomes, highlighting also new putative NMT substrates.SVMyr is freely available through a user-friendly web server at https://busca.biocomp.unibo.it/lipipred.  相似文献   

15.
Myristoyl-CoA:protein N-myristoyltransferase (NMT) has recently been identified as a target for antiviral and antifungal therapy. Candida albicans is a dimorphic, asexual yeast that is a major cause of systemic fungal infections in immunosuppressed humans. Metabolic labeling studies indicate that C. albicans synthesizes one principal 20-kDa N-myristoyl-protein. The single copy C. albicans NMT gene (ca-NMT1) was isolated and encodes a 451-amino acid protein that has 55% identity with Saccharomyces cerevisiae NMT. C. albicans NMT1 is able to complement the lethal phenotype of S. cerevisiae nmt1 null mutants by directing efficient acylation of the approximately 12 endogenous N-myristoylproteins produced by S. cerevisiae. C. albicans NMT was produced in Escherichia coli, a prokaryote with no endogenous NMT activity. In vitro studies of purified E. coli-derived S. cerevisiae and C. albicans NMTs revealed species-specific differences in the kinetic properties of synthetic octapeptide substrates derived from known N-myristoylproteins. Together these data indicate that C. albicans and S. cerevisiae NMTs have similar yet distinct substrate specificities which may be of therapeutic significance.  相似文献   

16.
Morgan CR  Miglionico BV  Engen JR 《Biochemistry》2011,50(16):3394-3403
The HIV-1 accessory protein Nef is N-terminally myristoylated, and this post-translational modification is essential for Nef function in AIDS progression. Transfer of a myristate group from myristoyl coenzyme A to Nef occurs cotranslationally and is catalyzed by human N-myristoyltransferase 1 (NMT). To investigate the conformational effects of myristoylation on Nef structure as well as to probe the nature of the Nef:NMT complex, we investigated various forms of Nef with hydrogen exchange mass spectrometry. Conformational changes in Nef were not detected as a result of myristoylation, and NMT had no effect on deuterium uptake by Nef in a myrNef:NMT complex. However, myrNef binding did have an effect on NMT deuterium uptake. Major HX differences in NMT were primarily located around the active site, with more subtle differences, at the longer time points, across the structure. At the shortest time point, significant differences between the two states were observed in two regions which interact strongly with the phosphate groups of coenzyme A. On the basis of our results, we propose a model of the Nef:NMT complex in which only the myristoyl moiety holds the two proteins together in complex and speculate that perhaps NMT chaperones Nef to the membrane and thereby protects the myristic acid group from the cytosol rather than Nef operating through a myristoyl switch mechanism.  相似文献   

17.
18.
Myristoylation corresponds to the irreversible covalent linkage of the 14-carbon saturated fatty acid, myristic acid, to the N-terminal glycine of many eukaryotic and viral proteins. It is catalyzed by N-myristoyltransferase. Typically, the myristate moiety participates in protein subcellular localization by facilitating protein-membrane interactions as well as protein-protein interactions. Myristoylated proteins are crucial components of a wide variety of functions, which include many signalling pathways, oncogenesis or viral replication. Initially, myristoylation was described as a co-translational reaction that occurs after the removal of the initiator methionine residue. However, it is now well established that myristoylation can also occur post-translationally in apoptotic cells. Indeed, during apoptosis hundreds of proteins are cleaved by caspases and in many cases this cleavage exposes an N-terminal glycine within a cryptic myristoylation consensus sequence, which can be myristoylated. The principal objective of this review is to provide an overview on the implication of myristoylation in health and disease with a special emphasis on post-translational myristoylation. In addition, new advancements in the detection and identification of myristoylated proteins are also briefly reviewed.  相似文献   

19.
Cotranslational and posttranslational modifications are increasingly recognized as important in the regulation of numerous essential cellular functions. N-myristoylation is a lipid modification ensuring the proper function and intracellular trafficking of proteins involved in many signaling pathways. Arabidopsis thaliana, like human, has two tightly regulated N-myristoyltransferase (NMT) genes, NMT1 and NMT2. Characterization of knockout mutants showed that NMT1 was strictly required for plant viability, whereas NMT2 accelerated flowering. NMT1 impairment induced extremely severe defects in the shoot apical meristem during embryonic development, causing growth arrest after germination. A transgenic plant line with an inducible NMT1 gene demonstrated that NMT1 expression had further effects at later stages. NMT2 did not compensate for NMT1 in the nmt1-1 mutant, but NMT2 overexpression resulted in shoot and root meristem abnormalities. Various data from complementation experiments in the nmt1-1 background, using either yeast or human NMTs, demonstrated a functional link between the developmental arrest of nmt1-1 mutants and the myristoylation state of an extremely small set of protein targets. We show here that protein N-myristoylation is systematically associated with shoot meristem development and that SnRK1 (for SNF1-related kinase) is one of its essential primary targets.  相似文献   

20.
The lipidic modification of proteins has recently been shown to be of immense importance, although many of the roles of these modifications remain as yet unidentified. One of such key modifications occurring on several proteins is the covalent addition of a 14-carbon long saturated fatty acid, a process termed myristoylation. Myristoylation can occur during both co-translational protein synthesis and posttranslationally, confers lipophilicity to protein molecules, and controls protein functions. The protein myristoylation process is catalyzed by the enzyme N-myristoyltransferase (NMT), which exists as two isoforms: NMT1 and NMT2. NMT1 is essential for growth and development, during which rapid cellular proliferation is required, in a variety of organisms. NMT1 is also reported to be elevated in many cancerous states, which also involve rapid cellular growth, albeit in an unwanted and uncontrolled manner. The delineation of myristoylation-dependent cellular functions is still in a state of infancy, and many of the roles of the myristoylated proteins remain to be established. The development of cells of the leukocytic lineage represents a phase of rapid growth and development, and we have observed that NMT1 plays a role in this process. The current review outlines the roles of NMT1 in the growth and differentiation of the cells of leukocytic origin. The described studies clearly demonstrate the roles of NMT1 in the regulation of the developmental processes of the leukocytes cells and provide a basis for further research with the aim of unraveling the roles of protein myristoylation in both cellular and physiological context.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号