Biophysical Journal 60: 690-696 (1991)
© 1991 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Schoenberg, M Search for Related Content PubMed PubMed Citation Articles by Schoenberg, M

Effect of ionic strength on skinned rabbit psoas fibers in the presence of magnesium pyrophosphate.

Laboratory of Physical Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892.

ABSTRACT

The effect of ionic strength on the kinetics of myosin cross-bridges in the presence of the ATP analogue PP, has been examined. It was found that increasing ionic strength from moderate values (mu approximately 100 mM) to high values (mu approximately 200 mM) has three effects. It causes a big decrease in the half time for the force decay after a small stretch, it causes a significant decrease in the sigmoidicity of the nucleotide analogue concentration dependence of the "apparent rate constant" of force decay after a small stretch, and it causes a big decrease in the range of rate constants necessary to describe the multiexponential force decay. It causes the last of these by causing a much larger increase in the slowest rate constants of the decay than in the fastest rate constants. The results suggest that whereas the behavior of cross-bridges in the presence of ATP is well-described by the simple independent-head equilibrium cross-bridge model of Schoenberg (1985. Biophys. J. 48:467-475), cross-bridges in the presence of the ATP analogue PPi require the more complicated double-headed equilibrium cross-bridge model of Anderson and Schoenberg (1987. Biophys. J. 52: 1077-1082) to describe their behavior.