The interaction of melittin with troponin C.

Melittin has been found to interact with troponin C with high affinity in the presence of Ca2+. The association constant approaches in magnitude that for melittin and calmodulin. The interaction results in a shift to lower wavelengths of the emission band of Trp-19 of melittin and in an increased shielding of Trp-19 from quenching. A major increase occurs in the alpha-helical content of combined melittin. Formation of the complex inhibits tryptic hydrolysis of the connecting strand. The properties of fluorescent labels attached to Met-25 and to AEDANS-98 are altered as a result of the interaction. It is concluded that the combined melittin makes extensive contact with the connecting strand and adjacent portions of the N- and C-terminal lobes.