Interactions of the melanocortin-4 receptor with the peptide agonist NDP-MSH.
Bottom Line: For the first time, the interactions between the terminal regions of NDP-MSH and the receptor are described.The amino-terminus appears to be adjacent to a series of hydrophilic residues with novel interactions at Cys196 (TM5) and Asp189 (extracellular loop 2).These interactions are reminiscent of sequential ligand binding exhibited by the beta(2)-adrenergic receptor, with the former interaction being equivalent to the known interaction involving Ser204 of the beta(2)-adrenergic receptor.
Affiliation: School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.Show MeSH
Mentions: The key residues contained within the MC4R that were mutated to Cys include the tight acidic cluster in TM3 (Asp122 and Asp126) and the conserved family A residues (Leu106 and Ile125).55 Additionally, important residues believed to be located in the hydrophobic binding pocket on TM6 (His264), as well as the residue in the MC4R (Met292) that is equivalent to the residue involved in the binding of retinol to bovine rhodopsin (Lys296) (Fig. 2; Supplementary Material), were also mutated to Cys. Each of the aforementioned mutants was incubated with CuP in the presence of the NDP-MSH Cys peptide containing analogues 2, 5, 6, 7L, 7D, 8, 9, and 13 (Fig. 3). The degree of covalent cross-linking, as determined by Western blot analysis and chemiluminescence signal, is shown in Fig. 3. The intensity of the signal varies depending on the occupancy of the binding site by the biotinylated ligand. The results are discussed in detail below.
Affiliation: School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.