The Effect of Mutations in Tropomyosin on Their Susceptibility to Protease-Facilitated Digestion

Student Name: 
Amy Du
UCD Department: 
Department of Neurobiology, Physiology, and Behavior
UCD Mentor: 
Dr. Aldrin Gomes

Tropomyosin works in conjunction with the troponin complex to regulate muscle contraction and relaxation. It is an alpha-helical protein that extends over the actin’s myosin binding sites. When calcium binds troponin, troponin interacts with tropomyosin in a way that changes tropomyosin structure, allowing myosin to bind to actin. Tropomyosin mutations are known to cause hypertrophic and dilated cardiomyopathy. However, the pathway for this is unknown. Preliminary studies conducted on tropomyosin studied the presence of phosphorylation sites and the up or down regulation of their phosphorylation, suggesting a structural change in the mutants. The presence of phosphorylation sites on tropomyosin were recently found but the functions of these sites are not known. Altered phosphorylation levels are usually important in protein function. To explore if mutations or phosphorylation of tropomyosin affect its conformation digestion of different tropomyosins was carried out. Trypsin digestion of tropomyosin mutants compared to the wild type suggest that the change of a single amino acid sequence affects digestion, which may be related to the structure. Since structure dictates function, a change in shape suggests a change in function. The implications of these results allow us to see the potential mechanism (structural change) for which mutated tropomyosin proteins may cause cardiomyopathy.