| First Author | Guo X | Year | 1994 |
| Journal | J Biol Chem | Volume | 269 |
| Issue | 21 | Pages | 15210-6 |
| PubMed ID | 8195157 | Mgi Jnum | J:31198 |
| Mgi Id | MGI:78697 | Doi | 10.1016/s0021-9258(17)36593-6 |
| Citation | Guo X, et al. (1994) Mutagenesis of cardiac troponin I. Role of the unique NH2-terminal peptide in myofilament activation. J Biol Chem 269(21):15210-6 |
| abstractText | Phosphorylation of Ser residues in the NH2-terminal extension unique to cardiac troponin I (cTnI) is known to occur through protein kinase A and to alter myofilament Ca2+ activation (Robertson, S. P., Johnson, J. D., Holroyde, M. J., Kranias, E. G., Potter, J. D., and Solaro, R. J. (1982) J. Biol. Chem. 257, 260-263). Yet, how the NH2-terminal extension may itself affect thin filament Ca2+ signaling is unknown. To approach this question we have used molecular cloning, mutagenesis, and bacterial synthesis of a full-length cTnI and a truncated mutant (cTnI/NH2) missing the 32 amino acids. Using reconstituted preparations we could show no differences between cTnI and cTnI/NH2 either in inhibition of actomyosin ATPase activity, in Ca(2+)-reversible inhibitory activity, or in the relation between pCa and Ca2+ binding to the regulatory site of cTnC at either pH 7.0 or 6.5. There were also no significant differences at either pH in the pCa-MgATPase activity relation of myofibrils into which the various species of TnI has been exchanged. Our results indicate: 1) that phosphorylation most likely induces a new state of TnI activity rather than altering an intrinsic effect of the NH2-terminal peptide on Ca2+ activation; and 2) that domains outside the NH2-terminal extension are important with regard to differences in effects of acidic pH on Ca2+ activation on cardiac and skeletal myofilaments. |
