Kanazawa H, Horiuchi Y, Takagi M, Ishino Y, Futai M
J Biochem. 1980 Sep;88(3):695-703. doi: 10.1093/oxfordjournals.jbchem.a133022.
The defective coupling factor F1 ATPase from a mutant strain (KF11) of Escherichia coli was purified to a practically homogeneous form. The final specific activity of Mg2+-ATPase was 6-9 units/mg protein, which is about 10-15 times lower than that of F1 ATPase from the wild-type strain. The mutant F1 had a ratio of Ca2+-ATPase to Mg2+-ATPase of about 3.5, whereas the wild-type F1 had ratio of about 0.8. The mutant F1 was more unstable than wild-type F1: on storage at -80 degrees C for 2 weeks, about 80% of its activity (dependent on Ca2+ or Mg2+) was lost, whereas none of the activity of the wild-type F1 was lost. The following results indicate that the mutation is in the beta subunit. (i) High Mg2+-ATPase activity (about 20 units/mg protein) was reconstituted when the beta subunit from wild type F1 was added to dissociated mutant F1 and the mixture was dialyzed against buffer containing ATP and Mg2+. (ii) Low ATPase activity having the same ratio of Ca2+-ATPase to Mg2+-ATPase as the mutant F1 was reconstituted when a mixture of the beta subunit from the mutant F1 and the alpha and gamma subunits from wild-type F1 was dialyzed against the same buffer. (iii) Tryptic peptide analysis of the beta subunit of the mutant showed a difference in a single peptide compared with the wild-type strain.
从大肠杆菌突变株（KF11）中纯化出有缺陷的偶联因子F1 ATP酶，使其达到实际的均一形式。Mg2 + -ATP酶的最终比活性为6 - 9单位/毫克蛋白质，比野生型菌株的F1 ATP酶低约10 - 15倍。突变型F1的Ca2 + -ATP酶与Mg2 + -ATP酶的比率约为3.5，而野生型F1的比率约为0.8。突变型F1比野生型F1更不稳定：在-80℃储存2周后，其约80%的活性（依赖于Ca2 +或Mg2 +）丧失，而野生型F1的活性没有丧失。以下结果表明突变发生在β亚基上。（i）当将野生型F1的β亚基添加到解离的突变型F1中，并将混合物在含有ATP和Mg2 +的缓冲液中透析时，可重构出高Mg2 + -ATP酶活性（约20单位/毫克蛋白质）。（ii）当将突变型F1的β亚基与野生型F1的α和γ亚基的混合物在相同缓冲液中透析时，可重构出具有与突变型F1相同的Ca2 + -ATP酶与Mg2 + -ATP酶比率的低ATP酶活性。（iii）与野生型菌株相比，突变型β亚基的胰蛋白酶肽分析显示在单个肽段上存在差异。
