A modulatory role for the troponin T tail domain in thin filament regulation

Maytum, Robin and Geeves, Michael A. and Lehrer, Sherwin S. (2002) A modulatory role for the troponin T tail domain in thin filament regulation. Journal of Biological Chemistry, 277 (33). 29774-29780 . ISSN 0021-9258. (The full text of this publication is not available from this repository)

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Abstract

In striated muscle the force generating acto-myosin interaction is sterically regulated by the thin filament proteins tropomyosin and troponin (Tn), with the position of tropomyosin modulated by calcium binding to troponin. Troponin itself consists of three subunits, TnI, TnC, and TnT, widely characterized as being responsible for separate aspects of the regulatory process. TnI, the inhibitory unit is released from actin upon calcium binding to TnC, while TnT performs a structural role forming a globular head region with the regulatory TnI- TnC complex with a tail anchoring it within the thin filament. We have examined the properties of TnT and the TnT(1) tail fragment (residues 1-158) upon reconstituted actin-tropomyosin filaments. Their regulatory effects have been characterized in both myosin S1 ATPase and S1 kinetic and equilibrium binding experiments. We show that both inhibit the actin-tropomyosin-activated S1 ATPase with TnT(1) producing a greater inhibitory effect. The S1 binding data show that this inhibition is not caused by the formation of the blocked B-state but by significant stabilization of the closed C-state with a 10-fold reduction in the C- to M-state equilibrium, K(T), for TnT(1). This suggests TnT has a modulatory as well as structural role, providing an explanation for its large number of alternative isoforms.

Item Type: Article
Additional information: 0021-9258 (Print) Journal Article Research Support, Non-U.S. Gov't
Uncontrolled keywords: Animals Hydrolysis Kinetics Muscle, Skeletal/metabolism Protein Binding Rabbits Spectrometry, Fluorescence Troponin T/*metabolism
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences > Protein Science Group
Depositing User: Michael Geeves
Date Deposited: 04 Sep 2008 15:30
Last Modified: 20 May 2014 15:59
Resource URI: http://kar.kent.ac.uk/id/eprint/4008 (The current URI for this page, for reference purposes)
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