Bisphosphorylation of cardiac troponin I modulates the Ca2+‐dependent binding of myosin subfragment S1 to reconstituted thin filaments
- 8 April 1996
- journal article
- Published by Wiley in FEBS Letters
- Vol. 384 (1), 43-47
- https://doi.org/10.1016/0014-5793(96)00274-8
Abstract
We have reconstituted thin filaments comprising pyrene-labelled actin (pyr-actin), tropomyosin (Tm) and cardiac troponin (cTn). cTn was isolated in two defined phosphorylation states; completely dephosphorylated on all subunits and with only the cTnI subunit bisphosphorylated. The thin filament was saturated with cTn at a pyr-actin/Tm/cTn ratio of 7:1:1. The calcium-dependent binding of S1 to thin filaments was measured in a stopped-flow spectrophotometer and the dependence of the observed rate constant on [Ca2+] fitted to the Hill equation. The only significant difference between the two phosphorylation states of the filaments was a 0.36 decrease in the pCa50 on bisphosphorylation.Keywords
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