Neither Helix in the Coiled Coil Region of the Axle of F1-ATPase Plays a Significant Role in Torque Production
Neither Helix in the Coiled Coil Region of the Axle of F1-ATPase Plays a Significant Role in Torque Production
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DOI：
10.1529/biophysj.108.140061
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发表时间：
2008-11-15
影响因子：
3.4
通讯作者：
Kinosita, Kazuhiko, Jr.
中科院分区：
文献类型：
--
作者：
Hossain, Mohammad Delawar;Furuike, Shou;Kinosita, Kazuhiko, Jr.
F1-ATP酶是一种ATP驱动的旋转分子马达，其中中心γ亚基在由α（3）β（3）亚基组成的圆柱体内旋转。γ-亚基的氨基和羧基末端形成轴，这是一种深深穿透定子圆柱体的α-螺旋盘绕线圈。我们之前一步一步地截断了轴，从较长的羧基末端开始，然后在相同的水平上切割两个末端，导致旋转速度较慢但相当强大。在这里，我们研究的作用，每个螺旋的羧基端截短25-40个氨基酸残基。较长的截短严重损害了运动复合体的稳定性：40个缺失未能产生旋转复合体。然而，多达36个缺失，突变体产生了近一半的野生型扭矩，独立的截断长度的明显扭矩。时间平均旋转速度低，因为负载相关的绊脚石在120度的间隔，即使与饱和ATP。与我们以前的工作比较表明，一半的正常扭矩产生在定子的孔口。羧基末端的尖端增加了另一半，而轴中间的两个螺旋对扭矩的产生和催化的快速进展都没有多大贡献。整个轴的残余物在旋转中没有一个起特定的决定性作用。
F1-ATPase is an ATP-driven rotary molecular motor in which the central gamma-subunit rotates inside the cylinder made of alpha(3)beta(3) subunits. The amino and carboxy termini of the gamma-subunit form the axle, an alpha-helical coiled coil that deeply penetrates the stator cylinder. We previously truncated the axle step by step, starting with the longer carboxy terminus and then cutting both termini at the same levels, resulting in a slower yet considerably powerful rotation. Here we examine the role of each helix by truncating only the carboxy terminus by 25-40 amino-acid residues. Longer truncation impaired the stability of the motor complex severely: 40 deletions failed to yield rotating the complex. Up to 36 deletions, however, the mutants produced an apparent torque at nearly half of the wild-type torque, independent of truncation length. Time-averaged rotary speeds were low because of load-dependent stumbling at 120 degrees intervals, even with saturating ATP. Comparison with our previous work indicates that half the normal torque is produced at the orifice of the stator. The very tip of the carboxy terminus adds the other half, whereas neither helix in the middle of the axle contributes much to torque generation and the rapid progress of catalysis. None of the residues of the entire axle played a specific decisive role in rotation.