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 language | English (US) |
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Pages (from-to) | 30-39 |
Number of pages | 10 |
Journal | Pflugers Archiv European Journal of Physiology |
Volume | 438 |
Issue number | 1 |
DOIs | |
State | Published - 1999 |
Keywords
- Calcium
- Muscle
- Troponin C
ASJC Scopus subject areas
- Physiology