The Journal of General Physiology, Vol 89, 905-920, Copyright © 1987 by The Rockefeller University Press

ARTICLES

ADP binding to myosin cross-bridges and its effect on the cross-bridge detachment rate constants

M Schoenberg and E Eisenberg

We have studied the binding of adenosine diphosphate (ADP) to attached cross-bridges in chemically skinned rabbit psoas muscle fibers and the effect of that binding on the cross-bridge detachment rate constants. Cross-bridges with ADP bound to the active site behave very similarly to cross-bridges without any nucleotide at the active site. First, fiber stiffness is the same as in rigor, which presumably implies that, as in rigor, all the cross-bridges are attached. Second, the cross- bridge detachment rate constants in the presence of ADP, measured from the rate of decay of the force induced by a small stretch, are, over a time scale of minutes, similar to those seen in rigor. Because ADP binding to the active site does not cause an increase in the cross- bridge detachment rate constants, whereas binding of nucleotide analogues such as adenyl-5'-yl imidodiphosphate (AMP-PNP) and pyrophosphate (PPi) do, it was possible, by using ADP as a competitive inhibitor of PPi or AMP-PNP, to measure the competitive inhibition constant and thereby the dissociation constant for ADP binding to attached cross-bridges. We found that adding 175 microM ADP to 4 mM PPi or 4 mM AMP-PNP produces as much of a decrease in the apparent cross- bridge detachment rate constants as reducing the analogue concentration from 4 to 1 mM. This suggests that ADP is binding to attached cross- bridges with a dissociation constant of approximately 60 microM. This value is quite similar to that reported for ADP binding to actomyosin subfragment-1 (acto-S1) in solution, which provides further support for the idea that nucleotides and nucleotide analogues seem to bind about as strongly to attached cross-bridges in fibers as to acto-S1 in solution (Johnson, R.E., and P. H. Adams. 1984. FEBS Letters. 174:11- 14; Schoenberg, M., and E. Eisenberg. 1985. Biophysical Journal. 48:863- 871; Biosca, J.A., L.E. Greene, and E. Eisenberg. 1986. Journal of Biological Chemistry. 261:9793-9800).
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				D. A. Martyn, L. Smith, K. L. Kreutziger, S. Xu, L. C. Yu, and M. Regnier The Effects of Force Inhibition by Sodium Vanadate on Cross-Bridge Binding, Force Redevelopment, and Ca2+ Activation in Cardiac Muscle Biophys. J., June 15, 2007; 92(12): 4379 - 4390. [Abstract] [Full Text] [PDF]

				H. Schmitz, M. C. Reedy, M. K. Reedy, R. T. Tregear, and K. A. Taylor Tomographic Three-dimensional Reconstruction of Insect Flight Muscle Partially Relaxed by AMPPNP and Ethylene Glycol J. Cell Biol., November 3, 1997; 139(3): 695 - 707. [Abstract] [Full Text] [PDF]

				M. Sata, S. Sugiura, H. Yamashita, S.-i. Momomura, and T. Serizawa Coupling Between Myosin ATPase Cycle and Creatine Kinase Cycle Facilitates Cardiac Actomyosin Sliding In Vitro : A Clue to Mechanical Dysfunction During Myocardial Ischemia Circulation, January 15, 1996; 93(2): 310 - 317. [Abstract] [Full Text]

Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents