Functional analysis of troponin I regulatory domains in the intact myofilament of adult single cardiac myocytes

Margaret V. Westfall, Faris P. Albayya, Joseph M. Metzger

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Troponin I is the putative molecular switch for Ca2+-activated contraction within the myofilament of striated muscles. To gain insight into functional troponin I domain(s) in the context of the intact myofilament, adenovirus-mediated gene transfer was used to replace endogenous cardiac troponin I within the myofilaments of adult cardiac myocytes with the slow skeletal isoform or a chimera of the slow skeletal and cardiac isoforms. Efficient expression and myofilament incorporation were observed in myocytes with each exogenous troponin I protein without detected changes in the stoichiometry of other contractile proteins and/or sarcomere architecture. Contractile function studies in single, permeabilized myocytes expressing exogenous troponin I provided support for the presence of a Ca2+-sensitive regulatory domain in the carboxyl terminus of troponin I and a second, newly defined Ca2+-sensitive domain residing in the amino terminus of troponin I. Additional experiments demonstrated that the isoform-specific, acidic pH- induced contractile dysfunction in myocytes appears to lie in the carboxyl terminus of troponin I. Functional results obtained from adult cardiac myocytes expressing the chimera or isoforms of troponin I now define multiple troponin I regulatory domains operating in the intact myofilament and provide new insight into the Ca2+-sensitive properties of troponin I during contraction.

Original languageEnglish (US)
Pages (from-to)22508-22516
Number of pages9
JournalJournal of Biological Chemistry
Issue number32
StatePublished - Aug 6 1999

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Copyright 2007 Elsevier B.V., All rights reserved.


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