Calmodulin bridging of IQ motifs in myosin-V.
Ca(2+)-saturated calmodulin binds to double-length IQ lever-arm sequences from murine myosin-V, forming a 1:1 "bridging" complex with very high affinity, (K9d)<10 pM for double motifs, IQ34, IQ45 and IQ56). Such a 1:1 complex involves interaction of one calmodulin (CaM) molecule with two adjacent IQ-motifs, providing a molecular mechanism for the observed Ca(2+)-dependent CaM dissociation from the IQ-region. Structural considerations suggest that formation of the 1:1 complex requires a severe distortion of the lever-arm, potentially regulating functional motility. This would be consistent with a recent report of diverse, irregular shapes of the lever arm of myosin-V induced by the presence of Ca(2+).
Martin
Stephen R
SR
Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.
Bayley
Peter M
PM
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism*; D029721:Drosophila Proteins / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D024701:Myosin Type V / Q000737:chemistry* / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence; D017186:Titrimetry / Q000379:methods; D014364:Tryptophan / Q000737:chemistry
D001059:Apoproteins; D002147:Calmodulin; D029721:Drosophila Proteins; D010446:Peptide Fragments; D014364:Tryptophan; D024701:Myosin Type V; D002118:Calcium