Modulation of Thin Filament Activation of Myosin ATP Hydrolysis by N-Terminal Domains of Cardiac Myosin Binding Protein-C
Modulation of Thin Filament Activation of Myosin ATP Hydrolysis by N-Terminal Domains of Cardiac Myosin Binding Protein-C
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DOI：
10.1021/bi500787f
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发表时间：
2014-10-28
期刊：
影响因子：
2.9
通讯作者：
White, Howard D.
中科院分区：
文献类型：
--
作者：
Belknap, Betty;Harris, Samantha P.;White, Howard D.
我们已经使用酶动力学来研究人类和小鼠心脏MyBP-C（C 0 C1，C1 C2和C 0 C2）的N-末端结构域影响F-肌动蛋白和天然猪细丝激活肌球蛋白ATP水解的分子机制。cMyBP-C的N端结构域抑制F-肌动蛋白对肌球蛋白-S1 ATP酶的激活。然而，小鼠和人类C1 C2和C 0 C2产生双相激活和抑制作用的激活肌球蛋白ATP水解的天然心脏细丝。MyBP-C N-末端结构域与细丝的低比率激活肌球蛋白-S1 ATP水解，但较高比率抑制ATP水解，如单独使用F-肌动蛋白所观察到的。这些数据表明，低浓度的C1 C2和C 0 C2激活细丝的机制类似于僵硬肌球蛋白-S1，而较高浓度的抑制ATP酶速率竞争与肌球蛋白-S1-ADP-Pi的肌动蛋白和细丝的结合。与C 0 C2和C1 C2相反，C 0 C1结构域的激活作用是物种依赖性的：人C 0 C1激活肌动球蛋白-S1 ATP酶速率，但小鼠C 0 C1不产生显著的激活或抑制。在pC（a）> 8时，蛋白激酶A对C1和C2结构域之间的m-接头中的丝氨酸残基的磷酸化降低了huC 0 C2对细丝的激活，但在pC（a）= 4时对激活机制几乎没有影响。在肌节中，cMyBP-C与肌动蛋白的低比例预期有利于cMyBP-C的激活作用，同时使与肌球蛋白头竞争产生的抑制最小化。
We have used enzyme kinetics to investigate the molecular mechanism by which the N-terminal domains of human and mouse cardiac MyBP-C (C0C1, C1C2, and C0C2) affect the activation of myosin ATP hydrolysis by F-actin and by native porcine thin filaments. N-Terminal domains of cMyBP-C inhibit the activation of myosin-S1 ATPase by F-actin. However, mouse and human C1C2 and C0C2 produce biphasic activating and inhibitory effects on the activation of myosin ATP hydrolysis by native cardiac thin filaments. Low ratios of MyBP-C N-terminal domains to thin filaments activate myosin-S1 ATP hydrolysis, but higher ratios inhibit ATP hydrolysis, as is observed with F-actin alone. These data suggest that low concentrations of C1C2 and C0C2 activate thin filaments by a mechanism similar to that of rigor myosin-S1, whereas higher concentrations inhibit the ATPase rate by competing with myosin-S1-ADP-Pi for binding to actin and thin filaments. In contrast to C0C2 and C1C2, the activating effects of the C0C1 domain are species-dependent: human C0C1 activates actomyosin-S1 ATPase rates, but mouse C0C1 does not produce significant activation or inhibition. Phosphorylation of serine residues in the m-linker between the C1 and C2 domains by protein kinase-A decreases the activation of thin filaments by huC0C2 at pC(a) > 8 but has little effect on the activation mechanism at pC(a) = 4. In sarcomeres, the low ratio of cMyBP-C to actin is expected to favor the activating effects of cMyBP-C while minimizing inhibition produced by competition with myosin heads.