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Regulation of Limulus skeletal muscle contraction
Author(s) -
Ritter Oliver,
Haase Hannelore,
Morano Ingo
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00224-0
Subject(s) - limulus , contraction (grammar) , muscle contraction , skeletal muscle , chemistry , biophysics , horseshoe crab , medicine , anatomy , biology , evolutionary biology , ecology
Skeletal muscle contraction of Limulus polyphemus , the horseshoe crab, seemed to be regulated in a dual manner, namely Ca 2+ binding to the troponin complex as well phosphorylation of the myosin light chains (MLC) by a Ca 2+ /calmodulin‐dependent myosin light chain kinase. We investigated muscle contraction in Limulus skinned fibers in the presence of Ca 2+ and of Ca 2+ /calmodulin to find out which of the two mechanisms prevails in Limulus skeletal muscle contraction. Although skinned fibers revealed high basal MLC mono‐ and biphosphorylation levels (0.48 mol phosphate/mol 31 kDa MLC; 0.52 mol phosphate/mol 21 kDa MLC), the muscle fibers were fully relaxed at pCa 8. Upon Ca 2+ or Ca 2+ /calmodulin activation, the fibers developed force (357±78.7 mN/mm 2 ; 338±69.7 mN/mm 2 , respectively) while the MLC phosphorylation remained essentially unchanged. We conclude that Ca 2+ activation is the dominant regulatory mechanism in Limulus skeletal muscle contraction.