Gizzard Ca2+-independent myosin light chain kinase: Evidence in favor of the phosphorylation theory

M. P. Walsh, R. Bridenbaugh, W. G.L. Kerrick, D. J. Hartshorne

Research output: Contribution to journalArticle

26 Scopus citations

Abstract

Limited digestion of calmodulin (CaM)-dependent myosin light chain kinase from turkey gizzard with α-chymotrypsin in the presence of bound CaM generated an 80,000-dalton kinase fragment that was fully active in the absence of Ca2+. This kinase catalyzed specific Ca2+-independent phosphorylation of the 20,000-dalton light chain of myosin using isolated light chains, intact myosin, and actomyosin. Phosphorylation of myosin in the absence of Ca2+ allowed us to dissociate myosin phosphorylation from other potential Ca2+-dependent regulatory mechanisms, thus permitting an evaluation of the postulated central role of myosin phosphorylation in the regulation of smooth muscle contraction. Ca2+-independent myosin phosphorylation was found to cause loss of Ca2+ sensitivity of actin-activated myosin ATPase activity in a crude actomyosin preparation, and tension development in skinned smooth muscle fibers in the absence of Ca2+. Myosin phosphorylation is, therefore, the key event in actin activation of ATPase activity and initiation of contraction in skinned chicken gizzard fibers.

Original languageEnglish (US)
Pages (from-to)45-50
Number of pages6
JournalFederation Proceedings
Volume42
Issue number1
StatePublished - Jan 1 1983
Externally publishedYes

ASJC Scopus subject areas

  • Medicine(all)

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