Myosin light chain phosphorylation and the cross-bridge cycle at low substrate concentration in chemically skinned guinea pig Taenia coli.
Myosin light chain phosphorylation and the cross-bridge cycle at low substrate concentration in chemically skinned guinea pig Taenia coli.
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化学剥皮豚鼠大肠杆菌带状体中低底物浓度下的肌球蛋白轻链磷酸化和跨桥循环。
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发表时间：
1985
期刊：
影响因子：
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通讯作者：
A. Arner
中科院分区：
文献类型：
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作者：
P. Hellstrand;A. Arner
测定了化学剥皮豚鼠大肠带菌的力-速度关系、ATP周转率（JATP）和2万个D肌球蛋白轻链（LC20）的磷酸化水平。3.2 mM MgATP时LC20的相对磷酸化在pCa 9时松弛组织中为17%，在pCa 4.5时随着[Ca2+]的增加而增加，最大磷酸化量为67%。在pCa 4.5时，力依赖于MgATP浓度，在0.1 mM时产生半最大响应。在pCa 4.5时，MgATP LC20在0.1 mM时磷酸化38%。在0.1 mM MgATP下，JATP和最大缩短速度（Vmax）分别降低到3.2 mM MgATP时的32%和43%。因此，低mgatp抑制LC20磷酸化以及交叉桥相互作用的程度和速率。高水平的LC20磷酸化，独立于Ca2+和MgATP浓度，通过atp - γ - s处理获得。LC20硫代磷酸化后，在3.2 mM MgATP下的最大力没有变化，而在0.065 mM MgATP下，硫代磷酸化后的最大力为一半，而Ca2+激活后的最大力为0.13 mM。在低mgatp （0.1 mM）时，硫代磷酸化制剂的收缩与次最大Vmax（60%）和JATP（27%）相关。结果表明，当Ca2+和MgATP浓度变化时，LC20磷酸化与Ca2+激活收缩的力发展程度相关。然而，在低MgATP下，降低的力和交叉桥周转率主要是由MgATP对交叉桥循环的影响介导的，这与对LC20磷酸化的影响是分开的。
Force-velocity relations, rate of ATP turnover (JATP), and phosphorylation of the 20,000 D myosin light chains (LC20) were measured in chemically skinned guinea pig Taenia coli. Relative LC20 phosphorylation at 3.2 mM MgATP was 17% in relaxed tissues at pCa 9, and increased with force at increasing [Ca2+] to a maximum of 67% at pCa 4.5. Force at pCa 4.5 was dependent on the MgATP concentration with a half-maximal response at about 0.1 mM. At 0.1 mM MgATP LC20 phosphorylation at pCa 4.5 was 38%. Both JATP and the maximal shortening velocity (Vmax) were reduced in 0.1 mM MgATP, to 32% and 43%, respectively, of their values at 3.2 mM MgATP. Low-MgATP thus inhibits both LC20 phosphorylation and the extent and rate of cross-bridge interaction. High levels of LC20 phosphorylation, independent of Ca2+ and MgATP concentrations, were obtained by treatment with ATP-gamma-S. Maximal force at 3.2 mM MgATP after LC20 thiophosphorylation was unchanged, whereas halfmaximal force occurred at 0.065 mM MgATP after thiophosphorylation, compared to 0.13 mM after activation by Ca2+. The contraction in thiophosphorylated preparations at low-MgATP (0.1 mM) was associated with submaximal Vmax (60%) and JATP (27%). The results show that LC20 phosphorylation is correlated with the degree of force development in the Ca2+ activated contraction, both when Ca2+ and MgATP concentrations are varied. The reduced force and rate of crossbridge turnover in low MgATP are however primarily mediated by an influence of MgATP on the cross-bridge cycle, which is separate from the effect on LC20 phosphorylation.