Poster Presentation 2014 International Biophysics Congress

Calcium sensitive effects of a hypertrophic cardiomyopathy mutation in cardiac troponin by NMR (#626)

Phani Rekha Potluri 1 , Nicole M. Cordina 1 , Louise J. Brown 1
  1. Department of Chemistry and Biomolecular Sciences, Macquarie University, North Ryde, NSW, Australia

Contraction of cardiac muscle is regulated by Ca2+ ions binding to the Troponin protein complex. Located on the actin-tropomyosin thin filament, troponin is a heterotrimeric protein complex that consists of a highly conserved Ca2+ binding subunit (TnC), an inhibitory subunit (TnI), and a thin filament binding subunit (TnT). Force generation in cardiac muscle is triggered by binding of Ca2+ to TnC. It is this simple binding of Ca2+ which induces conformational changes within the TnC subunit that then relieve the inhibitory influence of TnI to promote the formation of the acto-myosin cross bridge. Many single point mutations within the cardiac troponin complex have been found to alter both contraction and relaxation events in the heart, resulting in cardiomyopathy and sometimes sudden cardiac death.  In this present study, we have focused on the L29Q mutation, the first FHC mutation discovered in cTnC. This mutation is located in the Ca2+ binding domain of TnC with physiological studies showing that Ca2+ binding properties are altered. Here we have used paramagnetic relaxation enhancement (PRE) NMR to assess the structural effects arising from the L29Q mutation that may contribute to the disease state. Using nitroxide spin labeled constructs of L29Q, long-range distances (up to 25Å) are obtained by PRE-NMR which are then used to obtain a detailed view of the effects of this mutation on the structure and dynamics of cTnC. This study shows that the PRE-NMR approach is a highly suitable tool that allows for the rapid examination of structural perturbations resulting from disease-causing mutations.