Effects of the N-terminal domains of myosin binding protein-C in an in vitro motility assay -: Evidence for long-lived cross-bridges
Effects of the N-terminal domains of myosin binding protein-C in an in vitro motility assay -: Evidence for long-lived cross-bridges
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DOI：
10.1074/jbc.m606949200
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发表时间：
2006-11-24
影响因子：
4.8
通讯作者：
Harris, Samantha P.
中科院分区：
文献类型：
--
作者：
Razumova, Maria V.;Shaffer, Justin F.;Harris, Samantha P.
肌球蛋白结合蛋白- c （MyBP-C）是一种粗丝蛋白，其在肌节内的确切功能尚不清楚。然而，最近来自心脏中缺乏MyBP-C的cMyBP-C敲除小鼠的证据表明，cMyBP-C通常会减慢过桥循环速率并降低肌细胞输出功率。为了研究cMyBP-C限制过桥循环动力学的可能机制，我们利用体外运动分析评估了重组MyBP-C n端结构域对重肌球蛋白（HMM）支持肌动蛋白丝运动能力的影响。在这里，我们展示了含有MyBP-C“基序”的cMyBP-C的n端结构域，这是一个类似于110个氨基酸的序列，在所有MyBP-C亚型中都是保守的，在纤维被最大激活的条件下（即，在没有细丝调节蛋白或存在肌钙蛋白和原肌球蛋白和高[Ca2+]的情况下），降低了肌动蛋白丝的速度。相比之下，在细丝滑动速度是次最大的条件下（即在肌钙蛋白和原肌球蛋白和低[Ca2+]存在的情况下），含有基模的蛋白质增加了丝速度。重组n端蛋白也与f -肌动蛋白结合，抑制溶液中肌动蛋白- hmm atp酶的速率。结果表明，MyBP-C的n端结构域通过降低过桥分离速率来减缓过桥循环动力学。
Myosin binding protein-C ( MyBP-C) is a thick-filament protein whose precise function within the sarcomere is not known. However, recent evidence from cMyBP-C knock-out mice that lack MyBP-C in the heart suggest that cMyBP-C normally slows cross-bridge cycling rates and reduces myocyte power output. To investigate possible mechanisms by which cMyBP-C limits cross-bridge cycling kinetics we assessed effects of recombinant N-terminal domains of MyBP-C on the ability of heavy meromyosin (HMM) to support movement of actin filaments using in vitro motility assays. Here we show that N-terminal domains of cMyBP-C containing the MyBP-C "motif," a sequence of similar to 110 amino acids, which is conserved across all MyBP-C isoforms, reduced actin filament velocity under conditions where filaments are maximally activated (i.e. either in the absence of thin filament regulatory proteins or in the presence of troponin and tropomyosin and high [Ca2+]). By contrast, under conditions where thin filament sliding speed is submaximal (i.e. in the presence of troponin and tropomyosin and low [Ca2+]), proteins containing the motif increased filament speed. Recombinant N-terminal proteins also bound to F-actin and inhibited acto-HMM ATPase rates in solution. The results suggest that N-terminal domains of MyBP-C slow cross-bridge cycling kinetics by reducing rates of cross-bridge detachment.