title: Protective hinge in insulin opens to enable its receptor engagement.
abstract: Insulin provides a classical model of a globular protein, yet how the hormone changes conformation to engage its receptor has long been enigmatic. Interest has focused on the C-terminal B-chain segment, critical for protective self-assembly in β cells and receptor binding at target tissues. Insight may be obtained from truncated "microreceptors" that reconstitute the primary hormone-binding site (α-subunit domains L1 and αCT). We demonstrate that, on microreceptor binding, this segment undergoes concerted hinge-like rotation at its B20-B23 β-turn, coupling reorientation of Phe(B24) to a 60° rotation of the B25-B28 β-strand away from the hormone core to lie antiparallel to the receptor's L1-β2 sheet. Opening of this hinge enables conserved nonpolar side chains (Ile(A2), Val(A3), Val(B12), Phe(B24), and Phe(B25)) to engage the receptor. Restraining the hinge by nonstandard mutagenesis preserves native folding but blocks receptor binding, whereas its engineered opening maintains activity at the price of protein instability and nonnative aggregation. Our findings rationalize properties of clinical mutations in the insulin family and provide a previously unidentified foundation for designing therapeutic analogs. We envisage that a switch between free and receptor-bound conformations of insulin evolved as a solution to conflicting structural determinants of biosynthesis and function.
authors.affiliation: Structural Biology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia;
authors.forename: John G
authors.initials: JG
authors.lastname: Menting
authors.affiliation: Departments of Biochemistry.
authors.forename: Yanwu
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Medicine, University of Chicago, Chicago, IL 60637;
authors.forename: Shu Jin
authors.initials: SJ
authors.lastname: Chan
authors.affiliation: Departments of Biochemistry.
authors.forename: Nelson B
authors.initials: NB
authors.lastname: Phillips
authors.affiliation: La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia;
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Smith
authors.affiliation: Departments of Biochemistry.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Whittaker
authors.affiliation: Departments of Biochemistry.
authors.forename: Nalinda P
authors.initials: NP
authors.lastname: Wickramasinghe
authors.affiliation: Departments of Biochemistry.
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Whittaker
authors.affiliation: Departments of Biochemistry.
authors.forename: Vijay
authors.initials: V
authors.lastname: Pandyarajan
authors.affiliation: Departments of Biochemistry.
authors.forename: Zhu-li
authors.initials: ZL
authors.lastname: Wan
authors.affiliation: Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195;
authors.forename: Satya P
authors.initials: SP
authors.lastname: Yadav
authors.affiliation: Oregon National Primate Research Center, Beaverton, OR 97006;
authors.forename: Julie M
authors.initials: JM
authors.lastname: Carroll
authors.affiliation: Physiology.
authors.forename: Natalie
authors.initials: N
authors.lastname: Strokes
authors.affiliation: Oregon National Primate Research Center, Beaverton, OR 97006;Department of Medicine, Oregon Health and Science University, Portland, OR 97239;
authors.forename: Charles T
authors.initials: CT
authors.lastname: Roberts
authors.affiliation: Medicine, and.
authors.forename: Faramarz
authors.initials: F
authors.lastname: Ismail-Beigi
authors.affiliation: Department of Medicine, University of Chicago, Chicago, IL 60637;
authors.forename: Wieslawa
authors.initials: W
authors.lastname: Milewski
authors.affiliation: Department of Medicine, University of Chicago, Chicago, IL 60637; dfsteine@midway.uchicago.edu michael.weiss@case.edu lawrence@wehi.edu.au.
authors.forename: Donald F
authors.initials: DF
authors.lastname: Steiner
authors.affiliation: International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India; and.
authors.forename: Virander S
authors.initials: VS
authors.lastname: Chauhan
authors.affiliation: Structural Biology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia;
authors.forename: Colin W
authors.initials: CW
authors.lastname: Ward
authors.affiliation: Departments of Biochemistry,Medicine, andBiomedical Engineering, Case Western Reserve University, Cleveland, OH 44106; dfsteine@midway.uchicago.edu michael.weiss@case.edu lawrence@wehi.edu.au.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Weiss
authors.affiliation: Structural Biology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia;Department of Medical Biology, University of Melbourne, Parkville, VIC 3010, Australia dfsteine@midway.uchicago.edu michael.weiss@case.edu lawrence@wehi.edu.au.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Lawrence
mesh_terms: D018360:Crystallography, X-Ray; D007328:Insulin / Q000378:metabolism*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D011972:Receptor, Insulin / Q000378:metabolism*
chemical_list: D007328:Insulin; D011972:Receptor, Insulin
keywords: diabetes mellitus; metabolism; protein structure; receptor tyrosine kinase; signal transduction
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