Differing ADP Release Rates from Myosin Heavy Chain Isoforms Define the Shortening Velocity of Skeletal Muscle Fibers

Stefan Weiss, Rosetta Rossi, Maria Antonietta Pellegrino, Roberto Bottinelli, Michael A. Geeves

Research output: Contribution to journalArticle

Abstract

To understand mammalian skeletal myosin isoform diversity, pure myosin isoforms of the four major skeletal muscle myosin types (myosin heavy chains I, IIA, IIX, and IIB) were extracted from single rat muscle fibers. The extracted myosin (1-2 μg/15-mm length) was sufficient to define the actomyosin dissociation reaction in flash photolysis using caged-ATP (Weiss, S., Chizhov, I., and Geeves, M. A. (2000) J. Muscle Res. Cell Motil. 21, 423-432). The ADP inhibition of the dissociation reaction was also studied to give the ADP affinity for actomyosin (KAD). The apparent second order rate constant of actomyosin dissociation gets faster (K1k+2 = 0.17 -0.26 μM-1.s-1), whereas the affinity for ADP is weakened (250-930 μM) in the isoform order I, IIA, IIX, IIB. Both sets of values correlate well with the measured maximum shortening velocity (V 0) of the parent fibers. If the value of KAD is controlled largely by the rate constant of ADP release (k-AD), then the estimated value of k-AD is sufficiently low to limit V 0. In contrast, [ATP]K1k+2 at a physiological concentration of 5 mM ATP would be 2.5-6 times faster than k-AD.

Original languageEnglish
Pages (from-to)45902-45908
Number of pages7
JournalJournal of Biological Chemistry
Volume276
Issue number49
DOIs
Publication statusPublished - Dec 7 2001

ASJC Scopus subject areas

  • Biochemistry

Fingerprint Dive into the research topics of 'Differing ADP Release Rates from Myosin Heavy Chain Isoforms Define the Shortening Velocity of Skeletal Muscle Fibers'. Together they form a unique fingerprint.

Cite this