Molecular Determinants of Ligand Binding to the Human Melanocortin-4 Receptor

详细信息    查看全文

• 作者：Ying-kui Yang ; Tung M. Fong ; Chris J. Dickinson ; Cheri Mao ; Ji-Yao Li ; Michael R. Tota ; Ralph Mosley ; Lex H. T. Van der Ploeg ; and Ira Gantz
• 刊名：Biochemistry
• 出版年：2000
• 出版时间：December 5, 2000
• 年：2000
• 卷：39
• 期：48
• 页码：14900 - 14911
• 全文大小：171K
• 年卷期：v.39,no.48(December 5, 2000)
• ISSN：1520-4995

文摘

To elucidate the molecular basis for the interaction of ligands with the human melanocortin-4receptor (hMC4R), agonist structure-activity studies and receptor point mutagenesis were performed.Structure-activity studies of [Nle⁴,D-Phe⁷]-mages/gifchars/alpha.gif" BORDER=0>-melanocyte stimulating hormone (NDP-MSH) identifiedD-Phe7-Arg8-Trp9 as the minimal NDP-MSH fragment that possesses full agonist efficacy at the hMC4R.In an effort to identify receptor residues that might interact with amino acids in this tripeptide sequence24 hMC4R transmembrane (TM) residues were mutated (the rationale for choosing specific receptor residuesfor mutation is outlined in the Results section). Mutation of TM3 residues D122 and D126 and TM6residues F261 and H264 decreased the binding affinity of NDP-MSH 5-fold or greater, thereby identifyingthese receptor residues as sites potentially involved in the sought after ligand-receptor interactions. Byexamination of the binding affinities and potencies of substituted NDP-MSH peptides at receptor mutants,evidence was found that core melanocortin peptide residue Arg8 interacts at a molecular level with hMC4RTM3 residue D122. TM3 mutations were also observed to decrease the binding of hMC4R antagonists.Notably, mutation of TM3 residue D126 to alanine decreased the binding affinity of AGRP (87-132), aC-terminal derivative of the endogenous melanocortin antagonist, 8-fold, and simultaneous mutationsD122A/D126A completely abolished AGRP (87-132) binding. In addition, mutation of TM3 residueD122 or D126 decreased the binding affinity of hMC4R antagonist SHU 9119. These results providefurther insight into the molecular determinants of hMC4R ligand binding.