Miki J, Takeyama M, Noumi T, Kanazawa H, Maeda M, Futai M
Arch Biochem Biophys. 1986 Dec;251(2):458-64. doi: 10.1016/0003-9861(86)90352-8.
Mutant genes for the gamma subunit of H+-translocating ATPase (H+-ATPase) were cloned from eight different strains of Escherichia coli isolated in this laboratory. Determination of their nucleotide sequences revealed that they are amber nonsense mutations: a Gln codon at position 15, 158, 227, 262, and 270, respectively, was replaced by a termination codon in these strains. As terminal Met is missing in the gamma subunit, these results indicate that these strains are capable of synthesizing fragments of gamma subunits of 13, 156, 225, 260, and 268 amino acid residues, respectively. Studies on the properties of membranes of these strains suggested the importance of the region between Gln 269 and the carboxyl terminus (residue 286) for forming a stable F1 complex with ATPase activity and the region between Gln 226 and Gln 261 for normal interaction of F1 with F0. The sequence from Gln 261 to Gln 269 also seemed to be important for stability of F1 assembly on the membranes. The high frequency of the nonsense mutations suggested that the number of essential residues is limited in this subunit. Comparison of the homologies of the amino acid sequences of the gamma subunits from four different sources confirmed this notion: 19% of amino acid residues are identically conserved in these four strains, and the conserved regions are the amino terminal and carboxyl terminal regions.
从本实验室分离得到的8种不同大肠杆菌菌株中克隆了H⁺转运ATP酶（H⁺-ATPase）γ亚基的突变基因。对其核苷酸序列的测定表明，它们是琥珀色无义突变：在这些菌株中，第15、158、227、262和270位的谷氨酰胺密码子分别被终止密码子取代。由于γ亚基中缺失了末端甲硫氨酸，这些结果表明这些菌株分别能够合成13、156、225、260和268个氨基酸残基的γ亚基片段。对这些菌株膜特性的研究表明，谷氨酰胺269与羧基末端（第286位残基）之间的区域对于形成具有ATP酶活性的稳定F1复合物很重要，而谷氨酰胺226与谷氨酰胺261之间的区域对于F1与F0的正常相互作用很重要。从谷氨酰胺261到谷氨酰胺269的序列对于F1在膜上组装的稳定性似乎也很重要。无义突变的高频率表明该亚基中必需残基的数量有限。对来自四个不同来源的γ亚基氨基酸序列同源性的比较证实了这一观点：在这四个菌株中，19%的氨基酸残基是完全保守的，保守区域是氨基末端和羧基末端区域。
