title: Molecular cloning of a myosin I beta isozyme that may mediate adaptation by hair cells of the bullfrog's internal ear.
abstract: The internal ear's sensory receptor, or hair cell, responds when stimuli deflect its mechanoreceptive hair bundle. As a hair cell adapts to sustained stimulation, mechanical adjustments within the bundle reset its position of sensitivity. Because several lines of experimentation suggest that a form of myosin I mediates adaptation, we endeavored to clone cDNAs encoding this motor molecule. By using degenerate oligonucleotide primers based upon the deduced amino acid sequence for mammalian myosin I beta, we performed reverse transcription and polymerase chain reactions (PCRs) to produce a candidate cDNA from polyadenylylated mRNA isolated from the frog's brain. The resultant product was used to probe a cDNA library, from which were isolated clones encoding an approximately 119-kDa isozyme of myosin I beta. PCR amplification disclosed the presence of mRNA encoding the same isozyme in tissue from the bullfrog's sacculus, an organ of the internal ear. When expressed as a bacterial fusion protein, a domain from the tail region of this form of myosin I was recognized by monoclonal antibodies that react with myosin I in hair bundles. This cloned approximately 119-kDa isozyme of myosin I is accordingly a candidate to be the motor molecule responsible for the adaptation of mechanoelectrical transduction by hair cells.
authors.affiliation: Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas 75235-9117.
authors.forename: A B
authors.initials: AB
authors.lastname: Metcalf
authors.forename: Y
authors.initials: Y
authors.lastname: Chelliah
authors.forename: A J
authors.initials: AJ
authors.lastname: Hudspeth
mesh_terms: D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D001921:Brain / Q000201:enzymology; D002417:Cattle; D003001:Cloning, Molecular; D017124:Conserved Sequence; D017931:DNA Primers; D015870:Gene Expression; D006199:Hair Cells, Auditory, Inner / Q000201:enzymology / Q000502:physiology*; D007527:Isoenzymes / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D009218:Myosins / Q000096:biosynthesis*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000302:isolation & purification / Q000378:metabolism; D011892:Rana catesbeiana; D051381:Rats; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D007527:Isoenzymes; D012333:RNA, Messenger; D009218:Myosins