Complexation and calcium-induced conformational changes in the cardiac troponin complex monitored by hydrogen/deuterium exchange and FT-ICR mass spectrometry

▶ The structural dynamics and the Ca-induced conformational changes of the cardiac isoform of troponin are revealed by comparing H/D exchange rate constants for TnC alone, the binary TnC:TnI complex, and the ternary TnC:TnI:TnT complex for Ca-free and Ca-saturated states. ▶ TnC:TnI and TnC:TnI:TnT complexes possess both highly flexible and very rigid domains. ▶ The N-terminal extension of TnI (specific to the cardiac isoform), the DE linker in TnC alone, and the mobile domain of TnI exhibit fast H/D exchange rates. ▶ The present results corroborate prior X-ray crystallography and NMR interpretations and also illuminate domains that were absent or not resolved in those experiments.