Locusta migratoria flight muscle troponin partially activates thin filament in a calcium‐dependent manner
Locusta migratoria flight muscle troponin partially activates thin filament in a calcium‐dependent manner
复制标题
DOI：
10.1111/imb.12763
复制
发表时间：
2022-01
影响因子：
2.6
通讯作者：
Hui-Fang Liang;Xiang-dong Li
中科院分区：
文献类型：
--
作者：
Hui-Fang Liang;Xiang-dong Li
肌钙蛋白复合物是调节横纹肌收缩的Ca ~（2+）感受器，由TnT、TnI和TnC三个亚基组成。不同亚型的TnI和TnC在飞蝗（Locusta migratoria）的胸背纵肌（飞行肌）和后腿伸肌（跳跃肌）中表达。飞行肌和跳跃肌中的主要Tn复合物分别为Tn-171（TnT 1/TnI 7/TnC 1）和Tn-153（TnT 1/TnI 5/TnC 3）。本研究制备了大量重组肌钙蛋白复合物和重组细丝，并研究了它们对细丝的调控作用。虽然Tn-171和Tn-153都以Ca 2+依赖的方式调节细丝，但Tn-171介导的Ca 2+激活程度显著低于Tn-153。我们证明，TnC 1和TnC 3，而不是TnI 5和TnI 7，是负责不同水平的细丝激活。TnC 1和TnC 3的突变表明，TnC 1介导的细丝激活的低水平可归因于TnC 1的EF-手-II中的非典型残基Leu 60。因此，我们建议，除了Ca 2+，其他的调节机制（S）所需的蝗虫飞行肌肉的充分激活。
The troponin (Tn) complex, the sensor for Ca2+ to regulate contraction of striated muscle, is composed of three subunits, that is, TnT, TnI and TnC. Different isoforms of TnI and TnC are expressed in the thorax dorsal longitudinal muscle (flight muscle) and the hind leg extensor tibiae muscle (jump muscle) of the migratory locust, Locusta migratoria. The major Tn complexes in the flight muscle and the jump muscle are Tn‐171 (TnT1/TnI7/TnC1) and Tn‐153 (TnT1/TnI5/TnC3), respectively. Here, we prepared a number of recombinant Tn complexes and the reconstituted thin filaments, and investigated their regulation on thin filament. Although both Tn‐171 and Tn‐153 regulate thin filament in a Ca2+‐dependent manner, the extent of Ca2+ activation mediated by Tn‐171 was significantly lower than that by Tn‐153. We demonstrated that TnC1 and TnC3, rather than TnI5 and TnI7, are responsible for the different levels of the thin filament activation. Mutagenesis of TnC1 and TnC3 shows that the low level of TnC1‐mediated thin filament activation can be attributed to the noncanonical residue Leu60 in the EF‐hand‐II of TnC1. We therefore propose that, in addition to Ca2+, other regulatory mechanism(s) is required for the full activation of locust flight muscle.