Characterisation of a mutant of barnacle troponin C lacking Ca2+- binding sites at positions II and IV

L. D. Allhouse, G. Guzman, T. Miller, Q. Li, J. D. Potter, C. C. Ashley

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

This study investigates a mutant barnacle troponin C (TnC) protein (BTnC2-4-) in which the Ca2+binding sites (sites II and IV) have been rendered non-functional. Eliminating Ca2+ binding at both Ca2+-binding sites of barnacle TnC did not prevent the incorporation of BTnC2-4- into TnC- depleted myofibrillar bundles, although, as expected, the mutant was not able to effect muscle regulation. We conclude that the Mg2+ involved in stabilising the interaction between TnC and TnI in the barnacle must bind at a separate location to the Ca2+-binding sites. Competition experiments between BTnC2-4- and wild-type barnacle TnC (BTnCWT) or the native isoform BTnC2 indicate that BTnC2-4- has an approximately fourfold higher affinity for barnacle TnI than BTnCWT but a lower affinity for TnI compared to BTnC2. These results indicate that disabling sites II and IV changes the affinity of BTnC2-4- for TnC-denuded barnacle myofibrils, altering the stability of the bond formed between TnC and the thin filament.

Original languageEnglish (US)
Pages (from-to)30-39
Number of pages10
JournalPflugers Archiv European Journal of Physiology
Volume438
Issue number1
DOIs
StatePublished - 1999

Keywords

  • Calcium
  • Muscle
  • Troponin C

ASJC Scopus subject areas

  • Physiology

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