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Switching of Troponin I: Ca2+ and Myosin-induced Activation of Heart Muscle
- Source :
-
Journal of Molecular Biology . Jul2004, Vol. 340 Issue 2, p295-305. 11p. - Publication Year :
- 2004
-
Abstract
- The principal task of the Ca2+ activation of striated muscle is the release of the troponin I (TnI) inhibitory region (TnI-I) from actin. TnI-I release facilitates the repositioning of tropomyosin across the actin surface and the formation of strong, force generating, actin-myosin cross-bridges. Full activation of the Ca2+ regulatory switch (CRS) requires two switching steps in cTnI: binding of the TnI regulatory region to hydrophobic sites in the N-domain of Ca2+-bound troponin C and release of the adjacent TnI-I from actin. Using Förster resonance energy transfer, we have examined the requirements for full activation of the cardiac CRS. In the presence of actin, both Ca2+ and strong cross-bridges are required for full activation. Actin desensitizes the CRS to Ca2+ and produces cooperativity in the Ca2+ activation of the CRS. Strong cross-bridges eliminate cooperativity and re-sensitize the CRS to Ca2+. We propose a kinetic scheme and a structural model to account for these findings. [Copyright &y& Elsevier]
- Subjects :
- *MYOCARDIUM
*TROPOMYOSINS
*MUSCLE proteins
*ACTOMYOSIN
Subjects
Details
- Language :
- English
- ISSN :
- 00222836
- Volume :
- 340
- Issue :
- 2
- Database :
- Academic Search Index
- Journal :
- Journal of Molecular Biology
- Publication Type :
- Academic Journal
- Accession number :
- 13390749
- Full Text :
- https://doi.org/10.1016/j.jmb.2004.04.046