Yeast Glutamine-fructose-6-phosphate Aminotransferase (Gfa1) Requires Methionine Aminopeptidase Activity for Proper Function

Saint Louis University, Сент-Луис, Michigan, United States
Journal of Biological Chemistry (Impact Factor: 4.57). 05/2005; 280(14):14356-60. DOI: 10.1074/jbc.M501059200
Source: PubMed


Methionine aminopeptidase (MetAP) catalyzes the co-translational processing of initiator methionine from nascent proteins.
A cellular requirement for MetAP activity is likely due to dysfunction of MetAP substrates that require methionine removal
for proper protein function. Glutamine-fructose-6-phosphate aminotransferase (Gfa1) is an essential enzyme in yeast that catalyzes
the first and rate-limiting step in hexosamine biosynthesis. The α-amino group of Gfa1 Cys-1 has been proposed to act as a
nucleophile in the catalytic mechanism. We used two mutational strategies to evaluate whether removal of initiator methionine,
catalyzed by MetAP, is required for Gfa1 function. Our results demonstrate that exposure of the α-amino group of Cys-1 is
required for normal Gfa1 function as failure to do so results in decreased enzyme activity and slow growth. Further, either
isoform of MetAP in yeast is sufficient for Gfa1 processing in vivo. These results are the first demonstration of an endogenous yeast protein that requires the exposure of the α-amino group
by MetAP action for normal function. Additionally, Gfa1 will be a relevant target in therapeutic or physiological applications
in which MetAP activity is inhibited.

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    • "The function of MetAP1 is still not described in Fusarium spp., a deletion, however, reduces growth in Saccharomyces cerevisiae [18,25,26]. In both, prokaryotes and eukaryotes the N-terminal methionine is often cleaved by methionine aminopeptidase encoded by the gene MetAP1 [18]. "
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    ABSTRACT: Fusarium graminearum sensu stricto (s.s.) is an ubiquitous pathogen of cereals. The economic impact of Fusarium head blight (FHB) is characterized by crop losses and mycotoxin contamination. Our objective was to associate SNP diversity within candidate genes with phenotypic traits. A total of 77 F. graminearum s.s. isolates was tested for severity of fungal infection (= aggressiveness) and deoxynivalenol (DON) production in an inoculated field experiment at two locations in each of two years. For seven genes known to control fungal growth (MetAP1, Erf2) or DON production (TRI1, TRI5, TRI6 TRI10 and TRI14) single nucleotides polymorphic sites (SNPs) were determined and evaluated for the extent of linkage disequilibrium (LD). Associations of SNPs with both phenotypic traits were tested using linear mixed models. Decay of LD was in most instances fast. Two neighboring SNPs in MetAP1 and one SNP in Erf2 were significantly (P < 0.05) associated with aggressiveness explaining proportions of genotypic variance (pG) of 25.6%, 0.5%, and 13.1%, respectively. One SNP in TRI1 was significantly associated with DON production (pG = 4.4). We argue that using the published sequence information of Fusarium graminearum as a template to amplify comparative sequence parts of candidate genes is an effective method to detect quantitative trait loci. Our findings underline the potential of candidate gene association mapping approaches to identify functional SNPs underlying aggressiveness and DON production for F. graminearum s.s populations.
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    • "A defect in removal of N-terminal methionine caused by MetAP2 inhibition might lead to aberrant levels of proteins important for cell proliferation and apoptosis [26] [27]. Non-proper processing of the N-terminal methionine residue by MetAP results in difference of the first N-terminal residue which may significantly alter the function or binding affinities of the molecules.. Decreasing activity of glutamine- fructose-6-phosphate aminotransferase [28]; and reduction in binding of interleukin-1beta to its receptor [29] by dysfunction of MetAP2 are evident. TNP-470, a derivative of fumagillin, has been shown to be safe and effective in the treatment of solid tumors and arthritis in several animal studies and preclinical trials [30] [31]. "
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    ABSTRACT: Methionine aminopeptidases (MetAP) are proteases which remove the N-terminal methionine from newly synthesized proteins. Associations of MetAP2 with tumor progression of different cancers have been repeatedly reported. We aim to determine if MetAP2 is expressed in cholangiocarcinomas (CCA) and investigate to see if it would be a useful therapeutic target. We evaluated MetAP2 expression by immunohistochemistry in 82 patients of intrahepatic CCA. MetAP2 was expressed in bile ducts to various degrees. It was occasionally expressed with weak staining in normal bile duct epithelium but was strikingly over-expressed in dysplastic bile duct epithelia, primary and metastatic CCA tissues (p < 0.001). The increased expression of MetAP2 in proliferating bile duct was evident. All metastatic tumors had stronger expression of MetAP2 than the corresponding primary tumors. Fumagillin, a MetAP2 specific inhibitor, significantly inhibited cell proliferation in dose dependent manner and the degree of growth inhibition was dependent on the amount of cellular enzyme. The present study highlights the involvement of MetAP2 in an early event of carcinogenesis of CCA. The findings represent the first description of increased MetAP2 expression in CCA. The inhibition of enzyme activity using MetAP2 inhibitors may be a potential strategy for long-term control of tumor development and progression in CCA patients.
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