A 1H NMR study of a ternary peptide complex that mimics the interaction between troponin C and troponin I.
The troponin I peptide N alpha-acetyl TnI (104-115) amide (TnIp) represents the minimum sequence necessary for inhibition of actomyosin ATPase activity of skeletal muscle (Talbot, J.A. & Hodges, R.S. 1981, J. Biol. Chem. 256, 2798-3802; Van Eyk, J.E. & Hodges, R.S., 1988, J. Biol. Chem. 263, 1726-1732; Van Eyk, J.E., Kay, C.M., & Hodges, R.S., 1991, Biochemistry 30, 9974-9981). In this study, we have used 1H NMR spectroscopy to compare the binding of this inhibitory TnI peptide to a synthetic peptide heterodimer representing site III and site IV of the C-terminal domain of troponin C (TnC) and to calcium-saturated skeletal TnC. The residues whose 1H NMR chemical shifts are perturbed upon TnIp binding are the same in both the site III/site IV heterodimer and TnC. These residues include F102, I104, F112, I113, I121, I149, D150, F151, and F154, which are all found in the C-terminal domain hydrophobic pocket and antiparallel beta-sheet region of the synthetic site III/site IV heterodimer and of TnC. Further, the affinity of TnIp binding to the heterodimer (Kd = 192 +/- 37 microM) was found to be similar to TnIp binding to TnC (48 +/- 18 microM [Campbell, A.P., Cachia, P.J., & Sykes, B.D., 1991, Biochem. Cell Biol. 69, 674-681]). The results indicate that binding of the inhibitory region of TnI is primarily to the C-terminal domain of TnC. The results also indicate how well the synthetic peptide heterodimer mimics the C-terminal domain of TnC in structure and functional interactions.
Slupsky
C M
CM
Department of Biochemistry, University of Alberta, Edmonton, Canada.
Shaw
G S
GS
Campbell
A P
AP
Sykes
B D
BD
D000595:Amino Acid Sequence; D000818:Animals; D004330:Drosophila / Q000378:metabolism; D006859:Hydrogen; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D011817:Rabbits; D017386:Sequence Homology, Amino Acid; D014336:Troponin / Q000737:chemistry* / Q000378:metabolism; D019209:Troponin C; D019210:Troponin I; D014422:Turkeys
D010455:Peptides; D014336:Troponin; D019209:Troponin C; D019210:Troponin I; D006859:Hydrogen