title: CIB1 and CaBP1 bind to the myo1c regulatory domain.
abstract: Myo1c is a member of the myosin-I family that binds phosphoinositides and links the actin cytoskeleton to cellular membranes. Recent investigations suggest that targeting of myo1c to some subcellular regions requires the binding of an unknown protein to the IQ motifs in the myo1c regulatory domain. We identify two myristoylated proteins that bind the myo1c regulatory domain: calcium-binding protein 1 (CaBP1) and calcium- and integrin-binding-protein-1 (CIB1). CIB1 and CaBP1 interact with myo1c in vivo as determined by pull-down experiments and fluorescence microscopy where the endogenously expressed proteins show extensive cellular colocalization with myo1c. CIB1 and CaBP1 bind to the myo1c IQ motifs in the regulatory domain where they compete with calmodulin for binding. CaBP1 has a higher apparent affinity for myo1c than CIB1, and both proteins better compete with calmodulin in the presence of calcium. We propose that these proteins may play a role in specifying subcellular localization of myo1c.
authors.affiliation: The Pennsylvania Muscle Institute, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, Philadelphia, PA, 19104-6085, USA.
authors.forename: Nanyun
authors.initials: N
authors.lastname: Tang
authors.forename: Tianming
authors.initials: T
authors.lastname: Lin
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: J Kevin
authors.initials: JK
authors.lastname: Foskett
authors.forename: E Michael
authors.initials: EM
authors.lastname: Ostap
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D019556:COS Cells; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D002522:Chlorocebus aethiops; D051379:Mice; D024461:Myosin Type I / Q000737:chemistry / Q000378:metabolism*; D016716:PC12 Cells; D017434:Protein Structure, Tertiary; D051381:Rats; D020703:ras GTPase-Activating Proteins / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D002147:Calmodulin; C491604:Cib1 protein, rat; C088340:Myo1c protein, rat; D020703:ras GTPase-Activating Proteins; D024461:Myosin Type I; C085577:Ca2+-binding protein-1