Regulatory implications of a novel mode of interaction of calmodulin with a double IQ-motif target sequence from murine dilute myosin V.

ABSTRACT: Apo-Calmodulin acts as the light chain for unconventional myosin V, and treatment with Ca(2+) can cause dissociation of calmodulin from the 6IQ region of the myosin heavy chain. The effects of Ca(2+) on the stoichiometry and affinity of interactions of calmodulin and its two domains with two myosin-V peptides (IQ3 and IQ4) have therefore been quantified in vitro, using fluorescence and near- and far-UV CD. The results with separate domains show their differential affinity in interactions with the IQ motif, with the apo-N domain interacting surprisingly weakly. Contrary to expectations, the effect of Ca(2+) on the interactions of either peptide with either isolated domain is to increase affinity, reducing the K(d) at physiological ionic strengths by >200-fold to approximately 75 nM for the

SUBMITTER: Martin SR 

PROVIDER: S-EPMC2373755 | biostudies-literature | 2002 Dec

REPOSITORIES: biostudies-literature