Ligand-induced conformational change in the minimized insulin receptor.
Within the class of insulin and insulin-like growth factor receptors, detailed information about the molecular recognition event at the hormone-receptor interface is limited by the absence of suitable co-crystals. We describe the use of a biologically active insulin derivative labeled with the NBD fluorophore (B29NBD-insulin) to characterize the mechanism of reversible 1:1 complex formation with a fragment of the insulin receptor ectodomain. The accompanying 40 % increase in the fluorescence quantum yield of the label provides the basis for a dynamic study of the hormone-receptor binding event. Stopped-flow fluorescence experiments show that the kinetics of complex formation are biphasic comprising a bimolecular binding event followed by a conformational change. Displacement with excess unlabeled insulin gave monophasic kinetics of dissociation. The rate data are rationalized in terms of available experiments on mutant receptors and the X-ray structure of a non-binding fragment of the receptor of the homologous insulin-like growth factor (IGF-1).
Schlein
M
M
Health Care Discovery, Novo Nordisk A/S, Novo Alle 1, DK 2880, Bagsvaerd, Denmark.
Havelund
S
S
Kristensen
C
C
Dunn
M F
MF
Kaarsholm
N C
NC
D017667:Adipocytes / Q000378:metabolism; D000818:Animals; D002942:Circular Dichroism; D005453:Fluorescence; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D051379:Mice; D008958:Models, Molecular; D011487:Protein Conformation; D011972:Receptor, Insulin / Q000737:chemistry* / Q000378:metabolism*; D013816:Thermodynamics
D007328:Insulin; D008024:Ligands; D011972:Receptor, Insulin; D005947:Glucose