Inactivation of arginyl-tRNA protein transferase by a bifunctional arsenoxide: identification of residues proximal to the arsenoxide site.
Inactivation of arginyl-tRNA protein transferase by a bifunctional arsenoxide: identification of residues proximal to the arsenoxide site.
复制标题
双功能氧化砷使精氨酰-tRNA 蛋白转移酶失活：识别接近氧化砷位点的残基。
DOI：
10.1021/bi00001a017
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发表时间：
1995
期刊：
影响因子：
2.9
通讯作者：
Pickart,CM
中科院分区：
文献类型：
--
作者：
Li,J;Pickart,CM
Revised Manuscript Received October 19, 1994® abstract: Aminoacyl-tRNA protein transferases catalyze (posttranslational) ammoacylation of specific protein N-termini, using aminoacyl-tRNA as substrate. This modification targetsthe protein for ATP-dependent degradation; in eukaryotes, degradation occurs in the ubiquitin-mediated pathway. The eukaryotic transferase, which catalyzes Arg transferto N-terminal Glu or Asp residues, is potently inhibited by phenylarsenoxides. The gene encoding Arg-tRNA protein transferase from the yeast Saccharomyces cerevisiae was subcloned and overexpressed in Escherichia coli to provide largeamounts of homogeneous protein for a molecular analysis of this inhibition. The bifunctional reagent para-[(bromoacetyl) amino]-phenylarsenoxide is a potent and irreversible inactivator of the yeast transferase; the arsenoxide moiety of the reagentdirects binding to the enzyme, while the alkyl halide moiety alkylates a residue (s) proximal to thearsenoxide site. One mole of 14C-labeled reagent was covalently incorporated during inactivation, with the side chain of Cys-315 representing the major site of alkylation. Mutation of Cys-315to Ala yielded a fully active enzyme which was still subject to stoichiometric, irreversible inactivation by the bifunctional arsenoxide. With the C315A-enzyme, the major fraction of the 14C-labeled bifunctional reagent was associated with the sidechain (s) of one or more of a stretch of Glu residues (Glu 339—341). These results show that phenylarsenoxides inhibit Arg-tRNA protein transferase by binding to a site that is either itself essential, or regulates an essential site, mechanism.Aminoacyl-tRNA protein transferases catalyze the transfer of specific amino acids from charged tRNA to N-termini of suitable proteins or peptides. In the resulting products, the amino acid is linked by a normal peptide bond to the substrate’s a-amino group (Kaji, 1968; Soffer, 1970). Although aminoacyl-tRNA protein transferases were first characterized more than 20 years ago, only recently has a physiological function been described for them, involving intracellular proteolysis (below). The transferases remain
