Crystal structure of a cytokine-binding region of gp130

The structure of the cytokine-binding homology region of the cell surface receptor gp130 has been determined by X-ray crystallography at 2.0 Angstrom resolution. The beta sandwich structure of the two domains conforms to the topology of the cytokine receptor superfamily. This first structure of an uncomplexed receptor exhibits a similar L-shaped quaternary structure to that of ligand-boumd family members and suggests a limited flexibility in relative domain orientation of some 3 degrees. The putative ligand-binding loops are relatively rigid, with a phenylalanine side chain similarly positioned to exposed aromatic residues implicated in ligand binding for other such receptors. The positioning and structure of the N-terminal portion of the polypeptide chain have implications for the structure and function of cytokine receptors, such as gp130, which contain an additional N-terminal immunoglobulin-like domain.