αα-原肌球蛋白卷曲螺旋从解折叠链的自组装动力学。
Kinetics of self-assembly of alpha alpha-tropomyosin coiled coils from unfolded chains.
作者信息
Mo J M, Holtzer M E, Holtzer A
机构信息
Department of Chemistry, Washington University, Saint Louis, MO 63130.
出版信息
Proc Natl Acad Sci U S A. 1991 Feb 1;88(3):916-20. doi: 10.1073/pnas.88.3.916.
The two-chain coiled-coil structural motif is found in fibrous muscle proteins and leucine zippers. Unfolding/refolding studies abound, but none establishes the time scale or mechanism of structural assembly from separated, unfolded chains. Stopped-flow circular dichroism studies of such refolding of alpha-tropomyosin chains are reported here. The backbone spectral region (222 nm) reveals a fast phase (less than 0.04 s), yielding an intermediate possessing approximately 70% of the equilibrium helix content. A subsequent slow phase is first order [k-1 (20 degrees C) = 1.67 s, Ea = 12.7 kcal.mol-1 (1 kcal = 4.18 kJ)], so dimerization is fast. The same rate constant characterizes folding in the Cys-190 crosslinked chains, so the intermediate has parallel and nearly registered chains. The tyrosine spectral region (280 nm) reveals only a fast phase, so these six chain sites are native in the intermediate.
两链卷曲螺旋结构基序存在于纤维状肌肉蛋白和亮氨酸拉链中。关于展开/重折叠的研究很多，但没有一项研究确定从分离的未折叠链进行结构组装的时间尺度或机制。本文报道了对α-原肌球蛋白链这种重折叠的停流圆二色性研究。主链光谱区域（222 nm）显示出一个快速相（小于0.04 s），产生一种中间体，其具有约70%的平衡螺旋含量。随后的慢相是一级反应[k-1（20℃）= 1.67 s，Ea = 12.7 kcal·mol-1（1 kcal = 4.18 kJ）]，因此二聚化很快。相同的速率常数表征了Cys-190交联链中的折叠，所以中间体具有平行且几乎对齐的链。酪氨酸光谱区域（280 nm）仅显示一个快速相，所以这六个链位点在中间体中是天然的。
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