Calcium sensitivity of the cross-bridge cycle of Myo1c, the adaptation motor in the inner ear

Adamek, Nancy and Coluccio, Lynne M. and Geeves, Michael A. (2008) Calcium sensitivity of the cross-bridge cycle of Myo1c, the adaptation motor in the inner ear. Proceedings of the National Academy of Sciences of the United States of America. , 105 (15). pp. 5710-5715. ISSN 0027-8424. (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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The class I myosin Myo1c is a mediator of adaptation of mechanoelectrical transduction in the stereocilia of the inner ear. Adaptation, which is strongly affected by Ca2+, permits hair cells under prolonged stimuli to remain sensitive to new stimuli. Using a Myo1c fragment (motor domain and one IQ domain with associated calmodulin), with biochemical and kinetic properties similar to those of the native molecule, we have performed a thorough analysis of the biochemical cross-bridge cycle. We show that, although the steady-state ATPase activity shows little calcium sensitivity, individual molecular events of the cross-bridge cycle are calcium-sensitive. Of significance is a 7-fold inhibition of the ATP hydrolysis step and a 10-fold acceleration of ADP release in calcium. These changes result in an acceleration of detachment of the cross-bridge and a lengthening of the lifetime of the detached M-ATP state. These data support a model in which slipping adaptation, which reduces tip-link tension and allows the transduction channels to close after an excitatory stimulus, is mediated by Myo1c and modulated by the calcium transient.

Item Type: Article
Additional information: 070021/United Kingdom Wellcome Trust DC008793/DC/United States NIDCD GM68080/GM/United States NIGMS Journal Article Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't United States
Uncontrolled keywords: molecular motor; myosin
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences > Protein Science Group
Depositing User: Jane Griffiths
Date Deposited: 18 Apr 2009 10:14
Last Modified: 28 Apr 2014 15:36
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