Conformational analysis of the thrombin receptor agonist peptides SFLLR and SFLLR-NH2 by NMR: evidence for a cyclic bioactive conformation.
1997
The conformational properties of the pentapeptide Ser-Phe-Leu-Leu-Arg (P5), a human thrombin receptor-derived sequence forming part of a tethered ligand which activates the thrombin receptor, and its more active amide derivative Ser-Phe-Leu-Leu-Arg-NH2 (P5-NH2), have been studied by proton NMR spectroscopy in dimethylsulfoxide. Measurements of nuclear Overhauser effects, performed using two-dimensional rotating frame nuclear Overhauser (ROESY) and one-dimensional nuclear Overhauser enhancement (NOE) spectroscopy, revealed that P5 exists mainly in an extended conformation. However, proton–proton 1D-NOEs between Phe CαH and Ser CαH, Leu3 CαH and Leu3 NH, and Leu4 CαH and Leu4 NH, as well as between the Ser and Arg sidechains, also implicated a minor conformer for P5 having a curved backbone and a near-cyclic structure. In contrast to P5, measurements of NOEs and ROEs for P5-NH2 revealed a more stabilized cyclic structure which may account for its higher biological potency. Thus strong interresidue sequential NH (i)–NH (i + 1) interactions, as well as C-terminal carboxamide to N-terminal side-chain interactions, i.e., Arg CONH2 to Phe ring and Arg CONH2 to Ser \(C_\alpha /C_{\beta \beta '} \), observed at lower levels of the ROESY spectrum, supported a curved backbone structure for SFLLR-NH2. Since the higher potaency P5-NH2 analogue adopts predominantly a cyclic structure, a cyclic bioactive conformation for thrombin receptor agonist peptides is suggested.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
29
References
13
Citations
NaN
KQI