Proteolysis of smooth muscle myosin light chain kinase. Formation of inactive and calmodulin-independent fragments.

Journal Article

Proteolysis by trypsin of gizzard myosin light chain kinase in the absence of Ca2+-calmodulin causes a biphasic effect on kinase activity. During the initial phase of proteolysis, Ca2+-calmodulin-dependent kinase activity is reduced over a thousand-fold. Further proteolysis, in the second phase, causes an increase in activity that is independent of Ca2+-calmodulin. Loss of activity is associated with the formation of a 64,000-dalton fragment. Calmodulin-independent activity is associated with the formation of a 61,000-dalton fragment. Procedures for the isolation of each fragment are outlined. Tryptic hydrolysis of the isolated 64,000-dalton peptide generates the 61,000-dalton peptide and increases calmodulin-independent activity. Km values for ATP and light chains for the native kinase and two fragments are the same, i.e. approximately 100 and 5 microM, respectively. Neither fragment binds to F-actin. Amino acid analyses of both fragments are given. Synthetic peptides corresponding to the calmodulin-binding regions of the smooth and skeletal muscle kinases are potent inhibitors of the 61,000-dalton fragment. These data demonstrate the existence of an inhibitory region that is suggested to be located between the active site and the calmodulin-binding site. Whether it is distinct from or at the N-terminal end of the calmodulin-binding site cannot be determined from these data.

Full Text

Duke Authors

Cited Authors

  • Ikebe, M; Stepinska, M; Kemp, BE; Means, AR; Hartshorne, DJ

Published Date

  • October 5, 1987

Published In

Volume / Issue

  • 262 / 28

Start / End Page

  • 13828 - 13834

PubMed ID

  • 3654638

Pubmed Central ID

  • 3654638

International Standard Serial Number (ISSN)

  • 0021-9258


  • eng

Conference Location

  • United States