Cain B D, Simoni R D
J Biol Chem. 1986 Aug 5;261(22):10043-50.
Mutations in the uncB gene which encodes the a subunit of F1F0-ATPase in Escherichia coli were isolated and characterized. Eight mutations caused premature polypeptide chain termination. Two mutations were single amino acid substitutions resulting in the replacements of serine 206 with leucine (ser-206----leu) and histidine 245 with tyrosine (his-245----tyr). The ser-206----leu mutation does not alter F1 binding and allows ATP driven membrane energization at a low level. Stripping of F1 from membranes containing the ser-206----leu mutation does not render the membranes permeable to protons indicating impaired proton conductivity. The his-245----tyr mutation also blocks Fo-mediated proton conduction but has normal F1 binding properties. F1 bound to membranes with both ser-206----leu and his-245----tyr mutant a subunits is sensitive to dicyclohexylcarbodiimide. Apparently, both missense mutations impair proton conduction without altering assembly of the F1F0-ATPase complex. The direct involvement of the a subunit in proton translocation is discussed.
分离并鉴定了大肠杆菌中编码F1F0 - ATP酶α亚基的uncB基因突变。八个突变导致多肽链提前终止。两个突变是单个氨基酸替换，分别导致丝氨酸206被亮氨酸取代（ser - 206→leu）以及组氨酸245被酪氨酸取代（his - 245→tyr）。ser - 206→leu突变不改变F1结合，并允许ATP在低水平驱动膜的能量化。从含有ser - 206→leu突变的膜上去除F1不会使膜对质子通透，表明质子传导受损。his - 245→tyr突变也阻断了F0介导的质子传导，但具有正常的F1结合特性。与ser - 206→leu和his - 245→tyr突变α亚基结合的F1对二环己基碳二亚胺敏感。显然，这两个错义突变在不改变F1F0 - ATP酶复合物组装的情况下损害了质子传导。文中讨论了α亚基在质子转运中的直接作用。
