New Insight into the Binding Mode of Peptide Ligands at Urotensin-II Receptor: Structure−Activity Relationships Study on P5U and Urantide

Abstract

Urotensin II (U-II) is a disulfide bridged peptide hormone identified as the ligand of a G protein-coupled receptor. Human U-II (H-Glu-Thr-Pro-Asp-c[Cys-Phe-Trp-Lys-Tyr-Cys]-Val-OH) has been described as the most potent vasoconstrictor compound identified to date. We have recently identified both a superagonist of hU-II termed P5U (H-Asp-c[Pen-Phe-Trp-Lys-Tyr-Cys]-Val-OH) and the compound termed urantide (H-Asp-c[Pen-Phe-DTrp-Orn-Tyr-Cys]-Val-OH), which is the most potent UT receptor peptide antagonist described to date. In the present study, we have synthesized several analogues of P5U and urantide in which the Asp(4) residue in N-terminus position was replaced with coded and noncoded amino acids. The replacement of the Asp(4) residue by Tic led to an analogue, compound 14, more potent as antagonist (pK(B) = 8.94) compared to urantide. Furthermore, a different SAR was observed for the P5U compared to the urantide analogues. NMR and docking studies revealed a different binding mode for the agonist and antagonist ligands which could explain the observed SAR.

International Union of Basic and Clinical Pharmacology. XCII. Urotensin II, Urotensin II–Related Peptide, and Their Receptor: From Structure to Function

“…Surface plasmon resonance assays show that UII and URP interact with ECL2 and ECL3 but not ECL1, whereas the antagonist urantide only binds ECL2 (Boivin et al, 2006). Docking studies confirm that UT agonists and antagonists 226 Vaudry et al differentially bind a UT model (Grieco et al, 2009). Solution structure of the human UT (281-300) segment by high-resolution NMR and molecular modeling in the presence of UII also shows the occurrence of physical interactions between UII and ECL3 (Boivin et al, 2008).…”

Structure–Activity Study of the Peptides P5U and Urantide by the Development of Analogues Containing Uncoded Amino Acids at Position 9

“…Micelle solution was used, as we have reported the NMR structure of hU-II and other UT agonists [18,23,24] and antagonist [25,26] in this medium.…”

Identification of transmembrane domain 1 & 2 residues that contribute to the formation of the ligand-binding pocket of the urotensin-II receptor

“…The GROMACS software suite [43] was used with the OPLS/AA forcefield [44][45][46] and GBSA implicit solvent model [47] to perform potential energy minimization and a molecular dynamic simulation of the UII/rUT receptor complex. Distance restraints based on previous photolabeling results [42,48] and docking experiments [49] were used to guide and orient UII docking inside the binding pocket. The distance restraints were implemented in the topology file using r0 = 0 Å , r1 = 7 Å and r2 = 12 Å between the Cb atoms of the corresponding residues, with a force constant of 3000 kJ/mol/ nm 2 .…”

“…We used I-TASSER to generate the homology model of the UT receptor. UII was positioned in the binding cavity based on previously identified contact points from photolabeling [42,48] and previous docking efforts [49]. We next performed a short restrained molecular dynamic (MD) simulation to refine the complex (Fig.…”