A kinase-related protein stabilizes unphosphorylated smooth muscle myosin minifilaments in the presence of ATP

V. P. Shirinsky*, A. V. Vorotnikov, K. G. Birukov, A. K. Nanaev, M. Collinge, T. J. Lukas, J. R. Sellers, D. M. Watterson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

111 Scopus citations

Abstract

An apparent paradox in smooth muscle biology is the ability of unphosphorylated myosin to maintain a filamentous structure in the presence of ATP in vivo, whereas unphosphorylated myosin filaments are depolymerized in vitro in the presence of ATP. This suggests that additional uncharacterized factors are required for the stabilization of myosin filaments in the presence of ATP. We report here that an abundant smooth muscle protein forms sedimentable complexes with unphosphorylated smooth muscle myosin, partially reverses the depolymerizing effect of ATP on unphosphorylated myosin, and promotes the assembly of minifilaments as revealed by electron microscopy. This protein is called kinase-related protein (KRP) because it is derived from a gene within the gene for myosin light chain kinase (MLCK) and has an amino acid sequence identical to the carboxyl-terminal domain of MLCK. Consistent with the results with purified KRP, deletion of the KRP domain within MLCK results in a diminished ability of MLCK to interact with unphosphorylated myosin. KRP binds to the heavy meromyosin fragment of myosin but not to myosin rod or fragments lacking the hinge region and light chains. Altogether, these results suggest that KRP may play a critical role in stabilizing unphosphorylated myosin filaments and that the KRP domain of MLCK may be important for subcellular targeting to filaments.

Original languageEnglish (US)
Pages (from-to)16578-16583
Number of pages6
JournalJournal of Biological Chemistry
Volume268
Issue number22
StatePublished - 1993

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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