Calcium-Induced Weakening of Skeletal Muscle Z-Disks
- 1 August 1982
- journal article
- research article
- Published by Oxford University Press (OUP) in The Journal of Biochemistry
- Vol. 92 (2) , 381-390
- https://doi.org/10.1093/oxfordjournals.jbchem.a133944
Abstract
Structural changes in the Z disk were sensitively detected by measuring fragmentation indexes of myofibrils. The Ca 2+ -induced weakening of Z disks and the Z-disk removal by muscle calpain could be clearly distinguished by using muscle calpastatin, an endogenous inhibitor of muscle calpain. The Ca 2+ -induced weakening of Z disks occurred without concomitant release of a-actinin and had maxima at 10 −4 m Ca 2+ and 45°C and a minimum at pH 6.5, while the Z-disk removal by calpain had similar optima to the caseinolytic activity of calpain, at 10 −3 m Ca 2+ , 20°C and pH 7.0. The Ca 2+ -induced weakening of Z disks is therefore not due to the proteolytic action of calpain. In postmortem muscle, moreover, the Ca 2+ -induced weakening of Z disks was inferred to be predominate over calpain proteolysis, and therefore to be the major factor in the characteristic weakening of Z disks.Keywords
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