title: Myo1c binds phosphoinositides through a putative pleckstrin homology domain.
abstract: Myo1c is a member of the myosin superfamily that binds phosphatidylinositol-4,5-bisphosphate (PIP(2)), links the actin cytoskeleton to cellular membranes and plays roles in mechano-signal transduction and membrane trafficking. We located and characterized two distinct membrane binding sites within the regulatory and tail domains of this myosin. By sequence, secondary structure, and ab initio computational analyses, we identified a phosphoinositide binding site in the tail to be a putative pleckstrin homology (PH) domain. Point mutations of residues known to be essential for polyphosphoinositide binding in previously characterized PH domains inhibit myo1c binding to PIP(2) in vitro, disrupt in vivo membrane binding, and disrupt cellular localization. The extended sequence of this binding site is conserved within other myosin-I isoforms, suggesting they contain this putative PH domain. We also characterized a previously identified membrane binding site within the IQ motifs in the regulatory domain. This region is not phosphoinositide specific, but it binds anionic phospholipids in a calcium-dependent manner. However, this site is not essential for in vivo membrane binding.
authors.affiliation: The Pennsylvania Muscle Institute and Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6085, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Hokanson
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Laakso
authors.forename: Tianming
authors.initials: T
authors.lastname: Lin
authors.forename: David
authors.initials: D
authors.lastname: Sept
authors.forename: E Michael
authors.initials: EM
authors.lastname: Ostap
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival; D004847:Epithelial Cells / Q000166:cytology; D036681:Fluorescence Recovery After Photobleaching; D007700:Kinetics; D050356:Lipid Metabolism; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D024461:Myosin Type I; D009218:Myosins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D017354:Point Mutation / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D013379:Substrate Specificity; D053835:Unilamellar Liposomes / Q000378:metabolism
chemical_list: C470422:Myo1c protein, mouse; D018129:Phosphatidylinositol Phosphates; D011993:Recombinant Fusion Proteins; D053835:Unilamellar Liposomes; D024461:Myosin Type I; D009218:Myosins