Calcium-independent activation of skeletal muscle fibers by a modified form of cardiac troponin C

A conformational change accompanying Ca2+ binding to troponin C (TnC) constitutes the initial event in contractile regulation of vertebrate striated muscle. We replaced endogenous TnC in single skinned fibers from rabbit psoas muscle with a modified form of cardiac TnC (cTnC) which, unlike native cT...

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Bibliographic Details
Published in:Biophysical journal 1993-05, Vol.64 (5), p.1632-1637
Main Authors: Hannon, J.D., Chase, P.B., Martyn, D.A., Huntsman, L.L., Kushmerick, M.J., Gordon, A.M.
Format: Article
Language:English
Subjects:
Animals
Binding Sites
Biological and medical sciences
Biophysical Phenomena
Biophysics
Calcium - metabolism
Cell physiology
Cysteine - chemistry
Fundamental and applied biological sciences. Psychology
In Vitro Techniques
Molecular and cellular biology
Muscle contraction
Muscle Contraction - physiology
Muscles - chemistry
Myocardium - chemistry
Rabbits
Troponin - chemistry
Troponin - isolation & purification
Troponin - physiology
Troponin C
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Summary:A conformational change accompanying Ca2+ binding to troponin C (TnC) constitutes the initial event in contractile regulation of vertebrate striated muscle. We replaced endogenous TnC in single skinned fibers from rabbit psoas muscle with a modified form of cardiac TnC (cTnC) which, unlike native cTnC, probably contains an intramolecular disulfide bond. We found that such activating TnC (aTnC) enables force generation and shortening in the absence of calcium. With aTnC, both force and shortening velocity were the same at pCa 9.2 and pCa 4.0. aTnc could not be extracted under conditions which resulted in extraction of endogenous TnC. Thus, aTnC provides a stable model for structural studies of a calcium binding protein in the active conformation as well as a useful tool for physiological studies on the primary and secondary effects of Ca2+ on the molecular kinetics of muscle contraction.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(93)81517-0