Active regions' setting of the extracellular ligand-binding domain of human interleukin-6 receptor

The reliable three dimensional (3-D) structure of the extracellular ligand- binding domain (V106-P322) of human interleukin-6 receptor (hIL-6R) has bee n constructed by means of computer-guided homology modeling techniques usin g the crystal structure of the extracellular ligand-binding region (K52-L25 1) of human growth hormone receptor (hGHR) as templet. The space location o f some key residues which influence the combination ability between the rec eptor and the ligand has been observed and the effects of point mutagenesis of the four conservative cysteine residues on the space conformation are a nalyzed. The results show that the space conformation of the side-chain car boxyl of E305 plays a key role in the ligand-binding ability. Furthermore, the space conformation of the side-chain carboxyl of E305 is very important for the electrostatic potential complementarity between hIL-6R and hIL-6 a ccording to the docking method.