Activation of four enzymes by two series of calmodulin mutants with point mutations in individual Ca2+ binding sites.

Journal Article

Activation of four target enzymes by two series of calmodulin Ca2+ binding site mutants has been examined. In each mutant, the conserved bidentate glutamate of one of the Ca2+ binding sites is mutated to glutamine or lysine. The enzymes studied were smooth and skeletal muscle myosin light chain kinases, adenylylcyclase, and plasma membrane Ca(2+)-ATPase. For the first three enzymes, the activation patterns with the two mutant series were very similar: mutation of site 4 was most deleterious, then site 2, site 3, and site 1. This ranking was observed previously in Ca2+ binding and Ca(2+)-induced conformational studies of these mutants. Thus the response of these enzymes is probably determined by the extent to which each mutant's competence to interact with target binding regions has been compromised. In contrast, for Ca(2+)-ATPase, mutants of sites 3 and 4 were much poorer activators than those of sites 1 and 2. Events beyond calmodulin binding and related to enzyme activation probably dictate this unusual activation pattern and also the anomalously poor activation of skeletal muscle myosin light chain kinase by site 1 mutant B1Q. Site 1 mutant B1K showed wild type activation of all four enzymes suggesting that in site 1, the lysine substitution can evoke the conformational changes associated with Ca2+ binding.

Full Text

Duke Authors

Cited Authors

  • Gao, ZH; Krebs, J; VanBerkum, MF; Tang, WJ; Maune, JF; Means, AR; Stull, JT; Beckingham, K

Published Date

  • September 25, 1993

Published In

Volume / Issue

  • 268 / 27

Start / End Page

  • 20096 - 20104

PubMed ID

  • 8376368

International Standard Serial Number (ISSN)

  • 0021-9258

Language

  • eng

Conference Location

  • United States