1spy

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REGULATORY DOMAIN OF HUMAN CARDIAC TROPONIN C IN THE CALCIUM-FREE STATE, NMR, 40 STRUCTURES

Contents 1 Overview 2 Disease 3 About this Structure 4 Reference

Overview

While calcium binding to troponin C (TnC) triggers the contraction of both skeletal and cardiac muscle, there is clear evidence that different mechanisms may be involved. For example, activation of heart myofilaments occurs with binding to a single regulatory site on TnC, whereas activation of fast skeletal myofilaments occurs with binding to two regulatory sites. The physiological difference between activation of cardiac and skeletal myofilaments is not understood at the molecular level due to a lack of structural details for the response of cardiac TnC to calcium. We determined the solution structures of the apo and calcium-saturated regulatory domain of human cardiac TnC by using multinuclear, multidimensional nuclear magnetic resonance spectroscopy. The structure of apo human cardiac TnC is very similar to that of apo turkey skeletal TnC even though there are critical amino acid substitutions in site I. In contrast to the case with the skeletal protein, the calcium-induced conformational transition in the cardiac regulatory domain does not involve an "opening" of the regulatory domain, and the concomitant exposure of a substantial hydrophobic surface area. This result has important implications with regard to potential unique aspects of the interaction of cardiac TnC with cardiac troponin I and of modification of cardiac myofilament regulation by calcium-sensitizer drugs.

Disease

Known diseases associated with this structure: Cardiomyopathy, dilated, 1Z OMIM:[191040], Cardiomyopathy, familial hypertrophic, 192600 (3) OMIM:[191040]

About this Structure

1SPY is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.

Reference

Calcium-induced structural transition in the regulatory domain of human cardiac troponin C., Spyracopoulos L, Li MX, Sia SK, Gagne SM, Chandra M, Solaro RJ, Sykes BD, Biochemistry. 1997 Oct 7;36(40):12138-46. PMID:9315850

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