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Spectrophotometric and kinetic studies on normal and thyrotoxic cardiac myosins.

Authors
  • Kaldor, G
Type
Published Article
Journal
Canadian journal of sport sciences = Journal canadien des sciences du sport
Publication Date
Sep 01, 1992
Volume
17
Issue
3
Pages
168–170
Identifiers
PMID: 1325254
Source
Medline
License
Unknown

Abstract

Kinetic and microcalorimetric methods were used to study the interaction of thyrotoxic (V1) and normal adult cardiac myosin (V3) with ATP. It was shown that the overall enthalpy and entropy change was larger in the interaction of ATP with the thyrotoxic than with the normal myosin. There is evidence that the observed enthalpy changes were generated by protein conformational changes connected to the sequential destabilization and restabilization of the prevalent, energetically favored conformation of the myosin molecule. The V1-ATP interaction created more entropy than the V3-ATP interaction, and also the thyrotoxic isomyosin required more activation energy than the normal protein to attain the activated state. All of these results indicated that the catalytic activity of the V1 myosin was thermodynamically less efficient than that of the V3 isoenzyme.

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