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Mapping the domain of troponin T responsible for the activation of actomyosin ATPase activity. Identification of residues involved in binding to actin.
- Source :
- Journal of Biological Chemistry; September 2000, Vol. 275 Issue: 36 p27513-9, 7p
- Publication Year :
- 2000
-
Abstract
- The in vitro Ca(2+) regulation of the actomyosin Mg(2+)-ATPase at physiological ratios of actin, tropomyosin, and troponin occurs only in the presence of troponin T. We have previously demonstrated that a polypeptide corresponding to the first 191 amino acids of troponin T (TnT-(1-191)) activates the actomyosin Mg(2+)-ATPase in the presence of tropomyosin. In order to further characterize this activation domain, we constructed troponin T fragments corresponding to residues 1-157 (TnT-(1-157)), 1-76 (TnT-(1-76)), 77-157 (TnT-(77-157)), 77-191 (TnT-(77-191)), and 158-191 (TnT-(158-191)). Assays using these fragments demonstrated the following: (a) residues 1-76 do not bind to tropomyosin or actin; (b) residues 158-191 bind to actin cooperatively but not to tropomyosin; (c) the sequence 77-157 is necessary for troponin interaction with residue 263 of tropomyosin; (d) TnT-(77-191) on its own activates the actomyosin ATPase activity as described previously for TnT-(1-191). TnT-(1-157), TnT-(1-76), TnT-(77-157), TnT-(158-191), and combinations of TnT-(158-191) with TnT-(1-157) or TnT-(77-157) showed no effect on the ATPase activity. We conclude that the activation of actomyosin ATPase activity is mediated by a direct interaction between amino acids 77 and 191 of troponin T, tropomyosin, and actin.
Details
- Language :
- English
- ISSN :
- 00219258 and 1083351X
- Volume :
- 275
- Issue :
- 36
- Database :
- Supplemental Index
- Journal :
- Journal of Biological Chemistry
- Publication Type :
- Periodical
- Accession number :
- ejs7242863
- Full Text :
- https://doi.org/10.1074/jbc.M002735200