Conformational requirements for Ca(2+)/calmodulin binding and activation of myosin light chain kinase.
Myosin light chain kinase contains a regulatory segment consisting of an autoinhibitory region and a calmodulin-binding sequence that folds back on its catalytic core to inhibit kinase activity. It has been proposed that alpha-helix formation may be involved in displacement of the regulatory segment and activation of the kinase by Ca(2+)/calmodulin. Proline mutations were introduced at putative non-interacting residues in the regulatory segment to disrupt helix formation. Substitution of proline residues immediately N-terminal of the Trp in the calmodulin-binding sequence had most significant effects on Ca(2+)/calmodulin binding and activation. Formation of an alpha-helix in this region upon Ca(2+)/calmodulin binding may be necessary for displacement of the regulatory segment allowing phosphorylation of myosin regulatory light chain.
Padre
R C
RC
Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75235-9040, USA.
Stull
J T
JT
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D002147:Calmodulin / Q000737:chemistry / Q000378:metabolism*; D002522:Chlorocebus aethiops; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000737:chemistry; D009154:Mutation; D009219:Myosin-Light-Chain Kinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011392:Proline / Q000235:genetics; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary
D002147:Calmodulin; D011392:Proline; D009219:Myosin-Light-Chain Kinase; D002118:Calcium