Crystal structure of human insulin-like growth factor-1: detergent binding inhibits binding protein interactions.
Despite efforts spanning considerably more than a decade, a high-resolution view of the family of proteins known as insulin-like growth factors (IGFs) has remained elusive. IGF-1 consists of three helical segments which are connected by a 12-residue linker known as the C-region. NMR studies of members of this family reveal a dynamic structure with a topology resembling insulin but little structural definition in the C-region. We have crystallized IGF-1 in the presence of the detergent deoxy big CHAPS, and determined its structure at 1.8 A resolution by multiwavelength anomalous diffraction, exploiting the anomalous scattering of a single bromide ion and six of the seven sulfur atoms of IGF-1. The structure reveals a well-defined conformation for much of the C-region, which extends away from the core of IGF-1 and has residues known to be involved in receptor binding prominently displayed in a type II beta-turn. In the crystal, these residues form a dimer interface, but analytical ultracentrifugation experiments demonstrate that at physiological concentrations IGF-1 is monomeric. A single detergent molecule contacts residues known to be important for IGF-1 binding protein (IGFBP) interactions. Biophysical and biochemical data show that the detergent binds to IGF-1 specifically and blocks binding of IGFBP-1 and IGFBP-3.
Vajdos
F F
FF
Department of Protein Engineering, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, USA.
Ultsch
M
M
Schaffer
M L
ML
Deshayes
K D
KD
Liu
J
J
Skelton
N J
NJ
de Vos
A M
AM
D002793:Cholic Acids / Q000737:chemistry; D003461:Crystallography; D003902:Detergents / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000378:metabolism; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry
D002793:Cholic Acids; D003902:Detergents; D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; C436713:N,N-bis(3-gluconamidopropyl)deoxycholamide; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I