title: Interaction mechanism of insulin-like peptide 5 with relaxin family peptide receptor 4.
abstract: Insulin-like peptide 5 (INSL5) is a gut peptide hormone belonging to the insulin/relaxin superfamily. It is implicated in the regulation of food intake and glucose homeostasis by activating relaxin family peptide receptor 4 (RXFP4). Previous studies have suggested that the B-chain is important for INSL5 activity against RXFP4. However, functionalities of the B-chain residues have not yet been systematically studied. In the present work, we conducted alanine-scanning mutagenesis of the B-chain residues of human INSL5 to obtain an overview of their contributions. Binding and activation assays of these INSL5 mutants with human RXFP4 identified two essential exposed B-chain C-terminal residues (B23Arg and B24Trp) and one important exposed central B-chain residue (B16Ile). These three determinant residues together with the C-terminal carboxylate moiety probably constitute a central receptor-binding patch that forms critical hydrophobic and electrostatic interactions with RXFP4 during INSL5 binding. Some other exposed residues, including B10Glu, B12Ile, B13Arg, B17Tyr, B21Ser, and B22Ser, made minor contributions to INSL5 function. These auxiliary residues are scattered around the edge of the central receptor-binding patch, and thus form a peripheral receptor-binding patch on the surface of INSL5. Our present work provides new insights into the interaction mechanism of INSL5 with its receptor RXFP4.
authors.affiliation: Research Center for Translational Medicine at East Hospital, College of Life Sciences and Technology, Tongji University, Shanghai, China.
authors.forename: Meng-Jun
authors.initials: MJ
authors.lastname: Hu
authors.affiliation: Research Center for Translational Medicine at East Hospital, College of Life Sciences and Technology, Tongji University, Shanghai, China.
authors.forename: Dian
authors.initials: D
authors.lastname: Wei
authors.affiliation: Research Center for Translational Medicine at East Hospital, College of Life Sciences and Technology, Tongji University, Shanghai, China.
authors.forename: Xiao-Xia
authors.initials: XX
authors.lastname: Shao
authors.affiliation: Research Center for Translational Medicine at East Hospital, College of Life Sciences and Technology, Tongji University, Shanghai, China.
authors.forename: Jia-Hui
authors.initials: JH
authors.lastname: Wang
authors.affiliation: Research Center for Translational Medicine at East Hospital, College of Life Sciences and Technology, Tongji University, Shanghai, China.
authors.forename: Ya-Li
authors.initials: YL
authors.lastname: Liu
authors.affiliation: Research Center for Translational Medicine at East Hospital, College of Life Sciences and Technology, Tongji University, Shanghai, China.
authors.forename: Zeng-Guang
authors.initials: ZG
authors.lastname: Xu
authors.affiliation: Research Center for Translational Medicine at East Hospital, College of Life Sciences and Technology, Tongji University, Shanghai, China. Electronic address: zhan-yun.guo@tongji.edu.cn.
authors.forename: Zhan-Yun
authors.initials: ZY
authors.lastname: Guo
mesh_terms: D000409:Alanine / Q000737:chemistry; D020816:Amino Acid Motifs; D002942:Circular Dichroism; D005947:Glucose / Q000378:metabolism; D006706:Homeostasis; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D016296:Mutagenesis; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D018000:Receptors, Peptide / Q000378:metabolism*
chemical_list: D007328:Insulin; C084797:Leydig insulin-like protein; D011506:Proteins; C480239:RXFP4 protein, human; D043562:Receptors, G-Protein-Coupled; D018000:Receptors, Peptide; D005947:Glucose; D000409:Alanine
keywords: Activation; Binding; INSL5; Mutagenesis; RXFP4