Modulation of the oligomerization state of the bovine F1-ATPase inhibitor protein, IF1, by pH
Modulation of the oligomerization state of the bovine F1-ATPase inhibitor protein, IF1, by pH
复制标题
DOI：
10.1074/jbc.m003859200
复制
发表时间：
2000-08-18
影响因子：
4.8
通讯作者：
Walker, JE
中科院分区：
文献类型：
--
作者：
Cabezon, E;Butler, PJG;Walker, JE
牛IF 1是一种由84个氨基酸组成的碱性蛋白质，它参与ATP合成酶F-1结构域催化活性的调节。在pH 6.5时，它抑制ATP合成酶的ATP水解酶活性，但在碱性pH值时不抑制。通过沉降平衡分析超离心和共价交联研究了牛LF在不同pH值下的低聚状态。这两种技术都证实，蛋白质在pH 8时形成四聚体，而在pH 6.5以下，蛋白质主要是二聚体。通过共价交联，已经发现，在pH 8.0时，由残基44-84组成的IF片段形成二聚体，而来自残基32-84的片段是四聚体。因此，在位置32和43之间的一些或所有残基是四聚体形成所必需的，并且参与二聚体和四聚体之间的pH敏感性相互转化，在相互转化中的一个重要残基是组氨酸49，该残基突变为赖氨酸消除了pH依赖性活化-失活，并且突变蛋白在所研究的所有pH值下都是活性的和二聚体的。MMR研究可能表明，抑制剂蛋白通过在其C-末端区域形成反平行α-螺旋卷曲螺旋而二聚化，并且在高pH值下，当蛋白质为四聚体时，抑制区域被掩蔽。预测组氨酸49突变为赖氨酸将消除残基32-43上的卷曲螺旋形成，从而防止两个二聚体之间的相互作用，迫使平衡朝向二聚体状态，从而释放N-末端抑制区域并允许它们与F-1相互作用。
Bovine IF1, a basic protein of 84 amino acids, is involved in the regulation of the catalytic activity of the F-1 domain of ATP synthase, At pH 6.5, but not at basic pH values, it inhibits the ATP hydrolase activity of the enzyme. The oligomeric state of bovine LF, has been investigated at various pH values by sedimentation equilibrium analytical ultracentrifugation and by covalent cross-linking. Both techniques confirm that the protein forms a tetramer at pH 8, and below pH 6.5, the protein is predominantly dimeric, By covalent cross-linking, it has been found that at pH 8.0 the fragment of IF, consisting of residues 44-84 forms a dimer, whereas the fragment from residues 32-84 is tetrameric. Therefore, some or all of the residues between positions 32 and 43 are necessary for tetramer formation and are involved in the pH-sensitive interconversion between dimer and tetramer, One important residue in the interconversion is histidine 49, Mutation of this residue to lysine abolishes the pH-dependent activation-inactivation, and the mutant protein is active and dimeric at all pH values investigated. It is likely from MMR studies that the inhibitor protein dimerizes by forming an antiparallel alpha-helical coiled-coil over its C-terminal region and that at high pH values, where the protein is tetrameric, the inhibitory regions are masked. The mutation of histidine 49 to lysine is predicted to abolish coiled-coil formation over residues 32-43 preventing interaction between two dimers, forcing the equilibrium toward the dimeric state, thereby freeing the N-terminal inhibitory regions and allowing them to interact with F-1.