title: Identification of the single specific IQ motif of myosin V from which calmodulin dissociates in the presence of Ca2+.
abstract: Each heavy chain of dimeric chick brain myosin V (BMV) has a neck domain consisting of six IQ motifs with different amino acid sequences. The six IQ motifs form binding sites for five calmodulin (CaM) molecules and one essential light chain (either 17 or 23 kDa). When the calcium concentration is high, a small fraction of the 10 total CaM molecules dissociates from one molecule of BMV, resulting in loss of actin-based motor activity. At low Ca2+ concentrations, two molecules of exogenous CaM associate with one molecule of CaM-released BMV. This suggests that there is a single specific IQ motif responsible for the calcium-induced dissociation of CaM. In this study, we identify the specific IQ motif to be IQ2, the second IQ motif when counted from the N-terminal end of the neck domain. In addition, we showed that the essential light chains do not reside on IQ1 and IQ2. These findings were derived from proteolysis of BMV at high Ca2+ concentrations specifically at the neck region and SDS-PAGE analyses of the digests.
authors.affiliation: Department of Physics, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Koide
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kinoshita
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Shin'ichiro
authors.initials: S
authors.lastname: Tanaka
authors.forename: Naoki
authors.initials: N
authors.lastname: Nagura
authors.forename: Gabriele
authors.initials: G
authors.lastname: Meyer zu Hörste
authors.forename: Atsushi
authors.initials: A
authors.lastname: Miyagi
authors.forename: Toshio
authors.initials: T
authors.lastname: Ando
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D020816:Amino Acid Motifs; D000818:Animals; D019921:Biotinylation; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002147:Calmodulin / Q000032:analysis / Q000378:metabolism*; D002417:Cattle; D002645:Chickens; D004591:Electrophoresis, Polyacrylamide Gel; D019286:Endopeptidase K / Q000378:metabolism; D024701:Myosin Type V / Q000737:chemistry* / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011817:Rabbits
chemical_list: D002147:Calmodulin; D010446:Peptide Fragments; D019286:Endopeptidase K; D024701:Myosin Type V; D002118:Calcium