title: Myo1c mutations associated with hearing loss cause defects in the interaction with nucleotide and actin.
abstract: Three heterozygous missense mutations in the motor domain of myosin 1c (Myo1c), which mediates adaptation in the inner ear, are associated with bilateral sensorineural hearing loss in humans. With transient kinetic analyses, steady-state ATPase and motility assays, and homology modeling, we studied the interaction of these mutants with nucleotide and actin using a truncated construct, Myo1c(1IQ-SAH), which includes an artificial lever arm. Results indicate that mutation R156W, near switch 1, affects the nucleotide-binding pocket and the calcium binding by disrupting switch 1 movement. Mutation V252A, in the K helix of the upper 50 kDa domain, showed reduced actin affinity consistent with disruption of communication between the actin- and nucleotide-binding sites. T380M, in a Myo1c-specific insert in the HO linker, displayed aberrant changes in most kinetic parameters and uncoupling of the ATPase from motility. These data allow for an interpretation of how these mutations might affect adaptation.
authors.affiliation: Department of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, UK.
authors.forename: Nancy
authors.initials: N
authors.lastname: Adamek
authors.forename: Michael A
authors.initials: MA
authors.lastname: Geeves
authors.forename: Lynne M
authors.initials: LM
authors.lastname: Coluccio
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000235:genetics / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics; D034381:Hearing Loss / Q000235:genetics*; D007700:Kinetics; D051379:Mice; D024461:Myosin Type I; D009218:Myosins / Q000235:genetics* / Q000502:physiology; D009711:Nucleotides / Q000378:metabolism*; D017354:Point Mutation; D011817:Rabbits; D018411:Spodoptera / Q000235:genetics
chemical_list: C470422:Myo1c protein, mouse; D009711:Nucleotides; D000251:Adenosine Triphosphatases; D024461:Myosin Type I; D009218:Myosins