Hara K Y, Noji H, Bald D, Yasuda R, Kinosita K, Yoshida M
Chemical Resources Laboratory, R-1, Tokyo Institute of Technology, Nagatsuta 4259, Yokohama 226-8503, Japan.
J Biol Chem. 2000 May 12;275(19):14260-3. doi: 10.1074/jbc.275.19.14260.
F(1)-ATPase is a rotary motor protein, and ATP hydrolysis generates torque at the interface between the gamma subunit, a rotor shaft, and the alpha(3)beta(3) substructure, a stator ring. The region of conserved acidic "DELSEED" motif of the beta subunit has a contact with gamma subunit and has been assumed to be involved in torque generation. Using the thermophilic alpha(3)beta(3)gamma complex in which the corresponding sequence is DELSDED, we replaced each residue and all five acidic residues in this sequence with alanine. In addition, each of two conserved residues at the counterpart contact position of gamma subunit was also replaced. Surprisingly, all of these mutants rotated with as much torque as the wild-type. We conclude that side chains of the DELSEED motif of the beta subunit do not have a direct role in torque generation.
F(1)-ATP酶是一种旋转马达蛋白，ATP水解在γ亚基（一个旋转轴）和α(3)β(3)亚结构（一个定子环）之间的界面处产生扭矩。β亚基保守酸性“DELSEED”基序的区域与γ亚基接触，并被认为参与扭矩产生。利用相应序列为DELSDED的嗜热α(3)β(3)γ复合物，我们将该序列中的每个残基和所有五个酸性残基替换为丙氨酸。此外，γ亚基对应接触位置的两个保守残基也分别被替换。令人惊讶的是，所有这些突变体都能产生与野生型一样大的扭矩进行旋转。我们得出结论，β亚基的DELSEED基序的侧链在扭矩产生中没有直接作用。
