Role of cardiac troponin I carboxy terminal mobile domain and linker sequence in regulating cardiac contraction
Role of cardiac troponin I carboxy terminal mobile domain and linker sequence in regulating cardiac contraction
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DOI：
10.1016/j.abb.2016.03.010
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发表时间：
2016-07-01
影响因子：
3.9
通讯作者：
Chase, P. Bryant
中科院分区：
文献类型：
--
作者：
Meyer, Nancy L.;Chase, P. Bryant
静息Ca 2+时横纹肌收缩的抑制依赖于细肌丝中肌钙蛋白I（TnI）的C-末端一半。人们的注意力主要集中在TnI内的短抑制肽（Ip）序列上，但结构研究和疾病相关突变的鉴定将重点扩大到包括TnI C末端的较大移动的结构域（Md）序列。对于Md在肌肉松弛中有效地发挥作用，可能需要与肌钙蛋白的核心以及原肌球蛋白紧密的机械偶联。我们产生了含有两种TnI构建体之一的重组人心肌肌钙蛋白：Md和肌钙蛋白其余部分之间的8个氨基酸接头（cTnI（Link 8）），或Md缺失（cTnI（1-163））。运动性测定显示，cTnI（Link 8）使重构细丝滑动的Ca 2+敏感性显著增加（与WT相比，速度-pCa关系的0.9 pCa单位漂移相似），并且当Md完全缺失时进一步增加（与1.4 pCa单位漂移相似）。心脏肌钙蛋白在舒张期Ca 2+关闭肌丝滑动的能力大部分（61%），但未被cTnI完全消除（1-163）。肌钙蛋白I的Md是完全抑制无负荷肌丝滑动所必需的，尽管肌钙蛋白的其他部分--可能包括IP--也是必需的。我们还证实肌钙蛋白I的Md不负责肌钙蛋白对肌动球蛋白循环的超激活。(C)2016 Elsevier Inc. All rights reserved.
Inhibition of striated muscle contraction at resting Ca2+ depends on the C-terminal half of troponin I (Tnl) in thin filaments. Much focus has been on a short inhibitory peptide (Ip) sequence within TnI, but structural studies and identification of disease-associated mutations broadened emphasis to include a larger mobile domain (Md) sequence at the C-terminus of TnI. For Md to function effectively in muscle relaxation, tight mechanical coupling to troponin's core-and thus tropomyosin-is presumably needed. We generated recombinant, human cardiac troponins containing one of two Tnl constructs: either an 8 amino acid linker between Md and the rest of troponin (cTn(Link8)), or an Md deletion (cTnI(1-163)). Motility assays revealed that Ca2+-sensitivity of reconstituted thin filament sliding was markedly increased with cTnI(Link8) (similar to 0.9 pCa unit leftward shift of speed-pCa relation compared to WT), and increased further when Md was missing entirely (similar to 1.4 pCa unit shift). Cardiac Tn's ability to turn off filament sliding at diastolic Ca2+ was mostly (61%), but not completely eliminated with cTnI(1-163). TnI's Md is required for full inhibition of unloaded filament sliding, although other portions of troponin-presumably including Ip-are also necessary. We also confirm that TnI's Md is not responsible for superactivation of actomyosin cycling by troponin. (C) 2016 Elsevier Inc. All rights reserved.