论文
论文题目: Calmodulin in Complex with the First IQ Motif of Myosin-5a Functions as an Intact Calcium Sensor
论文题目英文:
作者: 沈梅①,张宁①,#郑三多①,张文博,张海满,路则宽,#苏乾,#孙育杰,#叶克穷,李向东*
论文出处:
年: 2016
卷: 113
期: 40
页: E5812-E5820
联系作者: 李向东
发表期刊: Proc Natl Acad Sci U S A
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论文连接 http://www.pnas.org/content/113/40/E5812
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摘要: The motor function of vertebrate myosin-5a is inhibited by its tail in a Ca2+-dependent manner. We previously demonstrated that the calmodulin (CaM) bound to the first isoleucine-glutamine (IQ) motif (IQ1) of myosin-5a is responsible for the Ca2+-dependent regulation of myosin-5a. We have solved the crystal structure of a truncated myosin-5a containing the motor domain and IQ1 (MD-IQ1) complexed with Ca2+-bound CaM (Ca2+-CaM) at 2.5-Å resolution. Compared with the structure of the MD-IQ1 complexed with essential light chain (an equivalent of apo-CaM), MD-IQ1/Ca2+-CaM displays large conformational differences in IQ1/CaM and little difference in the motor domain. In the MD-IQ1/Ca2+-CaM structure, the N-lobe and the C-lobe of Ca2+-CaM adopt an open conformation and grip the C-terminal and the N-terminal portions of the IQ1, respectively. Remarkably, the interlobe linker of CaM in IQ1/Ca2+-CaM is in a position opposite that in IQ1/apo-CaM, suggesting that CaM flip-flops relative to the IQ1 during the Ca2+ transition. We demonstrated that CaM continuously associates with the IQ1 during the Ca2+ transition and that the binding of CaM to IQ1 increases Ca2+ affinity and substantially changes the kinetics of the Ca2+ transition, suggesting that the IQ1/CaM complex functions as an intact Ca2+ sensor responding to distinct calcium signals.
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