The influence of myosin converter and relay domains on cross-bridge kinetics of Drosophila indirect flight muscle.
The influence of myosin converter and relay domains on cross-bridge kinetics of Drosophila indirect flight muscle.
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肌球蛋白转换器和中继域对果蝇间接飞行肌过桥动力学的影响。
DOI：
10.1016/j.bpj.2010.06.047
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发表时间：
2010
影响因子：
3.4
通讯作者：
Swank,DouglasM
中科院分区：
文献类型：
--
作者：
Yang,Chaoxing;Kaplan,CharlotteN;Thatcher,MariaL;Swank,DouglasM
我们正在调查的转换器和继电器域的肌动球蛋白跨桥循环的基本速率常数的影响。转换器和中继结构域之间的变化drosophilamyosin重链异构体由于选择性mRNA剪接。以前，我们发现，单独插入胚胎肌球蛋白异构体（EMB）的版本，这些域到间接飞行肌（IFM）肌球蛋白异构体（IFI）都降低果蝇IFM的权力和减缓肌肉动力学。为了确定变化背后的跨桥机制，我们采用正弦分析，而不同的磷酸盐和MgATP浓度skinnedDrosophilaIFM纤维。基于六态跨桥模型，EMB转换器降低了与肌动蛋白附着和功产生相关的肌球蛋白速率常数k4，但增加了与跨桥分离和功吸收相关的速率k2。相比之下，EMB中继域对动力学的影响很小，因为只有k4降低。主要的变化是机械的，在工作生产幅度下降。这两个领域decreasedk4支持的假设，这些领域是至关重要的，以手臂介导的力量的产生。这两个结构域显着影响MgATP亲和力。我们的模型表明，转换域是EMB和IFI肌球蛋白之间限速跨桥步骤差异的原因，即，肌球蛋白异构化与EMB的MgADP释放和IFI的Pi释放相关。
We are investigating the influence of the converter and relay domains on elementary rate constants of the actomyosin cross-bridge cycle. The converter and relay domains vary betweenDrosophilamyosin heavy chain isoforms due to alternative mRNA splicing. Previously, we found that separate insertions of embryonic myosin isoform (EMB) versions of these domains into the indirect flight muscle (IFM) myosin isoform (IFI) both decreasedDrosophilaIFM power and slowed muscle kinetics. To determine cross-bridge mechanisms behind the changes, we employed sinusoidal analysis while varying phosphate and MgATP concentrations in skinnedDrosophilaIFM fibers. Based on a six-state cross-bridge model, the EMB converter decreased myosin rate constants associated with actin attachment and work production,k4, but increased rates related to cross-bridge detachment and work absorption,k2. In contrast, the EMB relay domain had little influence on kinetics, because onlyk4decreased. The main alteration was mechanical, in that work production amplitude decreased. That both domains decreasedk4supports the hypothesis that these domains are critical to lever-arm-mediated force generation. Neither domain significantly influenced MgATP affinity. Our modeling suggests the converter domain is responsible for the difference in rate-limiting cross-bridge steps between EMB and IFI myosin—i.e., a myosin isomerization associated with MgADP release for EMB and Pi release for IFI.