Myosin light chain phosphorylation affects the structure of rabbit skeletal muscle thick filaments

被引:170
作者
Levine, RJC
Kensler, RW
Yang, ZH
Stull, JT
Sweeney, HL
机构
[1] UNIV PUERTO RICO,SCH MED,DEPT ANAT,SAN JUAN,PR
[2] UNIV PENN,SCH MED,DEPT PHYSIOL,PHILADELPHIA,PA 19104
[3] UNIV TEXAS,SW MED CTR,DEPT PHYSIOL,DALLAS,TX 75235
关键词
D O I
10.1016/S0006-3495(96)79293-7
中图分类号
Q6 [生物物理学];
学科分类号
071011 ;
摘要
To identify the structural basis for the observed physiological effects of myosin regulatory light chain phosphorylation in skinned rabbit skeletal muscle fibers (potentiation of force development at low calcium), thick filaments separated from the muscle in the relaxed state, with unphosphorylated light chains, were incubated with specific, intact, myosin light chain kinase at moderate (pCa 5.0) and low (pCa 5.8) calcium and with calcium-independent enzyme in the absence of calcium, then examined as negatively stained preparations, by electron microscopy and optical diffraction. All such experimental filaments became disordered (lost the near-helical array of surface myosin heads typical of the relaxed state), Filaments incubated in control media, including intact enzyme in the absence of calcium, moderate calcium (pCa 5.0) without enzyme, and bovine serum albumin substituting for calcium-independent myosin light chain kinase, all retained their relaxed structure. Finally, filaments disordered by phosphorylation regained their relaxed structure after incubation with a protein phosphatase catalytic subunit. We suggest that the observed disorder is due to phosphorylation-induced increased mobility and/or changed conformation of myosin heads, which places an increased population of them close to thin filaments, thereby potentiating actin-myosin interaction at low calcium levels.
引用
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页码:898 / 907
页数:10
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