Kinetic analysis of the slow skeletal myosin MHC-1 isoform from bovine masseter muscle
Kinetic analysis of the slow skeletal myosin MHC-1 isoform from bovine masseter muscle
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DOI：
10.1016/j.jmb.2007.08.050
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发表时间：
2007-11-09
影响因子：
5.6
通讯作者：
Geeves, M. A.
中科院分区：
文献类型：
--
作者：
Bloemink, M. J.;Adamek, N.;Geeves, M. A.
在肌纤维中发现了II类肌球蛋白的几种重链同种型，并显示出多种不同的机械活性。快速肌球蛋白（肌球蛋白重链（MHC）-II-2）收缩速度比慢速肌球蛋白（MHC-II-1，也称为β-肌球蛋白）更快，并且已经充分证实，MHC-II-1的ADP与肌动球蛋白的结合比MHC-II-2紧密得多。最近，我们报道了MHC-II亚型之间的其他一些差异。兔子的1和2亚型II-1不像II-2的肌动球蛋白的ATP的双相解离，ATP-裂解步骤是显着较慢的MHC-II-1和缓慢的亚型显示存在多个肌动球蛋白-ADP复合物。这些结果与发表的牛左心室肌MHC-II-1的数据相反，后者更类似于快速骨骼同种型。牛MHC-II-1是在心室肌和慢骨骼肌纤维如咬肌中表达的主要同种型，并且是心肌生理学参考工作的重要来源。这项工作检查和扩展牛MHC-II-1的动力学。我们确认了对兔比目鱼肌MHC-II-1的工作的主要发现。重要的是，我们表明，在没有肌动蛋白的情况下，ADP对牛咬肌肌球蛋白的亲和力（由解离常数K-D表示）比最初描述的牛心肌肌球蛋白弱，因此ADP和肌动蛋白与肌球蛋白结合之间的热力学耦合要小得多（K-AD/K-D类似于5，而不是K-AD/K-D类似于50）。这可能表明这组肌球蛋白马达存在一种不同类型的机械化学偶联。我们还发现，牛MHC-II-1的ATP水解速率（19 s（-1））比以前报道的（138 s（-1））慢得多。我们将讨论这项工作如何融入更广泛的特征。肌球蛋白家族中的肌球蛋白马达。(C)2007爱思唯尔有限公司版权所有。
Several heavy chain isoforms of class II myosins are found in muscle fibres and show a large variety of different mechanical activities. Fast myosins (myosin heavy chain (MHC)-II-2) contract at higher velocities than slow myosins (MHC-II-1, also known as beta-myosin) and it has been well established that ADP binding to actomyosin is much tighter for MHC-II-1 than for MHC-II-2. Recently, we reported several other differences between MHC-II isoforms. 1 and 2 of the rabbit. Isoform II-1 unlike II-2 gave biphasic dissociation of actomyosin by ATP, the ATP-cleavage step was significantly slower for MHC-II-1 and the slow isoforms showed the presence of multiple actomyosin-ADP complexes. These results are in contrast to published data on MHC-II-1 from bovine left ventricle muscle, which was more similar to the fast skeletal isoform. Bovine MHC-II-1 is the predominant isoform expressed in both the ventricular myocardium and slow skeletal muscle fibres such as the masseter and is an important source of reference work for cardiac muscle physiology. This work examines and extends the kinetics of bovine MHC-II-1. We confirm the primary findings from the work on rabbit soleus MHC-II-1. Of significance is that we show that the affinity of ADP for bovine masseter myosin in the absence of actin (represented by the dissociation constant K-D) is weaker than originally described for bovine cardiac myosin and thus the thermodynamic coupling between ADP and actin binding to myosin is much smaller (K-AD/K-D similar to 5 instead of K-AD/K-D similar to 50). This may indicate a distinct type of mechanochemical coupling for this group of myosin motors. We also find that the ATP-hydrolysis rate is much slower for bovine MHC-II-1 (19 s(-1)) than reported previously (138 s(-1)). We discuss how this work fits into a broader characterisation. of myosin motors from across the myosin family. (C) 2007 Elsevier Ltd. All rights reserved.