An NMR, CD, Molecular Dynamics, and Fluorometric Study of the Conformation of the Bradykinin Antagonist B-9340 in Water and in Aqueous Micellar Solutions

Abstract

A detailed NMR, CD, fluorometry, and molecular modeling study of a novel bradykinin antagonist B-9340, containing a novel amino acid D-Igl (alpha-(2-indanyl)glycine) at position 7, was carried out. The sequence of B-9340 is D-Arg0-Arg1-Pro2-Hyp3-Gly4-Thi5-Ser6-D- Igl7-Oic8-Arg9, where Hyp is hydroxyproline, Thi is beta-(2-thienyl)alanine, and Oic is (3aS,7aS)-octahydroindole-2-carboxylic acid. The CD results exhibit a striking effect of SDS on the spectrum of the BK antagonist, indicating that interaction with the surfactant induces a folded peptide structure. The interaction of this antagonist with phosphatidylinositol was monitored by fluorometry, indicating that the interaction of the peptide with the lipid is cooperative, and gives a Hill coefficient of 2.3. The two-dimensional proton NMR measurements indicate that B-9340 has no stable secondary structure in water solution and contains about 10-15% cis peptide bonds arising from Pro2, Hyp3, and Oic8. In SDS micelles, NMR reveals the existence of two beta-turns based on a number of medium-range connectivities that were useful for molecular modeling. The actual molecular modeling and dynamic runs were performed on B-9340 in an environment consisting of a layer of octyl sulfate anions and water. Ther results indicate that the structure of B-9340 in a micellar environment is characterized by a nonideal betaII-turn comprising residues Pro2 to Thi5, a nonideal betaII'-turn comprising residues Ser6-Arg9, and broad folding in the middle part of the molecule. The structure is stabilized by several hydrogen bonds and by a salt bridge between the guanidine moiety of Arg1 and the carboxyl group of Arg9, whereas the middle part of the peptide is buried in the micelle. The structure is deposited as Brookhaven PDB file 1 BDK.

An NMR Study of the Interaction of 15N‐Labelled Bradykinin with an Antibody Mimic of the Bradykinin B2 Receptor

“…Large numbers of bradykinin analogues have been synthesized and tested for biological activity (Stewart and Vavrek, 1991;Stewart, 1995) and a number of these analogues have been studied by NMR free in solution (Kyle et al, 1993;Otter et al, 1993;Liu et al, 1993;Guba et al, 1994;Sejbal et al, 1996). Such studies have resulted in qualitative statements about likely conformational features of bradykinin bound to the B2 receptor but, with one exception, detailed bradykinin structures which could be compared with the present data have not been reported.…”

Interaction and structural study of kinin peptide bradykinin and ganglioside monosialylated 1 micelle

“…A random extended conformation in water solution for bradykinin is in good agreement with other observations for bradykinin and its agonists and antagonists. 2,18 Our previous reported data of CD spectrum of BK in water indicated a random coil structure. 19 A short dynamics run performed with BK immersed in water in the absence of any constraints showed a large molecular flexibility (data not shown).…”

“…2,3 It plays many roles in pathophysiology, particularly as an initiator of inflammation. 4,5 This peptide exerts biological effects by binding to specific G-protein-coupled receptors 6 (B2) on the cell membrane, thereby triggering a series of poorly understood biochemical events that are manifested by pain, 7 contraction of smooth muscle, lowering of arterial pressure, 8 etc.…”

An NMR Conformational Analysis of Cyclic Bradykinin Mimics. Evidence for a β-Turn

“…The resonance assignments for BKM-824, BKM-870, and BKM-872 are given in Tables II, III, and IV, respectively. The assignment of the Oic cross peaks was accomplished with the aid of the TOCSY and ROESY experiments as well as an analogy with data from the literature (3,4). A single HMQC experiment was performed for BKM-824 to aid in the assignment of Oic and Ava.…”