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

George M. Bou-Assaf, Jean E. Chamoun, Mark R. Emmett, Piotr G. Fajer, Alan G. Marshall

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

Cardiac muscle contraction is regulated by the heterotrimeric complex: troponin. We apply solution-phase hydrogen/deuterium exchange monitored by FT-ICR mass spectrometry to study the structural dynamics and the Ca-induced conformational changes of the cardiac isoform of troponin, 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. The wide range of exchange rate constants indicates that the complexes possess both highly flexible and very rigid domains. Fast exchange rates were observed for the N-terminal extension of TnI (specific to the cardiac isoform), the DE linker in TnC alone, and the mobile domain of TnI. The slowest rates were for the IT coiled-coil that grants stability and stiffness to the complex. Ca2+ binding to site II of the N-lobe of TnC induces short-range allosteric effects, mainly protection for the C-lobe of TnC that transmits long-range conformational changes that reach the IT coiled-coil and even TnT1. The present results corroborate prior X-ray crystallography and NMR interpretations and also illuminate domains that were truncated or not resolved in those experiments.

Original languageEnglish (US)
Pages (from-to)116-124
Number of pages9
JournalInternational Journal of Mass Spectrometry
Volume302
Issue number1-3
DOIs
StatePublished - Apr 30 2011

Keywords

  • FTMS
  • Fourier transform
  • H/D exchange
  • Ion cyclotron resonance
  • Isotopic depletion

ASJC Scopus subject areas

  • Instrumentation
  • Condensed Matter Physics
  • Spectroscopy
  • Physical and Theoretical Chemistry

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