ABSTRACTEra is an essential GTPase inEscherichia coli, and Era has been implicated in a number of cellular functions. Homologues of Era have been identified in various bacteria and some eukaryotes. Using theeragene as bait in the yeast two-hybrid system to screenE. coligenomic libraries, we discovered that Era interacts with MazG, a protein of unknown function which is highly conserved among bacteria. The direct interaction between Era and MazG was also confirmed in vitro, being stronger in the presence of GDP than in the presence of GTPγS. MazG was characterized as a nucleoside triphosphate pyrophosphohydrolase which can hydrolyze all eight of the canonical ribo- and deoxynucleoside triphosphates to their respective monophosphates and PPi, with a preference for deoxynucleotides. AmazGdeletion strain ofE. coliwas constructed by replacing themazGgene with a kanamycin resistance gene. UnlikemutT, a gene for another conserved nucleotide triphosphate pyrophosphohydrolase that functions as a mutator gene, themazGdeletion did not result in a mutator phenotype inE. coli.
摘要Era 是大肠杆菌(Escherichia coli)中一种重要的 GTP 酶,Era 与多种细胞功能有关。目前已在多种细菌和一些真核生物中发现了 Era 的同源物。我们利用酵母双杂交系统中的 Eeragene 作为诱饵筛选大肠杆菌基因组文库,发现 Era 与 MazG 相互作用,MazG 是一种功能未知的蛋白质,在细菌中高度保守。我们还在体外证实了 Era 与 MazG 之间的直接相互作用,这种作用在 GDP 存在时比在 GTPγS 存在时更强。MazG 被鉴定为一种核苷三磷酸焦磷酸水解酶,可将所有八种核糖核苷和脱氧核苷三磷酸水解为各自的单磷酸和 PPi,并偏好脱氧核苷酸。通过用卡那霉素抗性基因替换 AmazG 基因,构建了大肠杆菌 AmazG 基因缺失株。与作为突变基因的另一种保守的核苷酸三磷酸焦磷酸水解酶基因mutT不同,AmazG缺失并没有导致大肠杆菌出现突变表型。