Tertiary structural models of human interleukin-6 and evaluation by comparison with X-ray and NMR structures.

Tertiary structure models of interleukin-6 were constructed using a routine prediction method based on the X-ray crystal structures of granulocyte colony-stimulating factor (GCSF) and leukemia inhibitory factor (LIF). Those models were evaluated using a sequence-structure compatibility (3D-1D) method program Compass and a limited amount of NMR distance information when it was concluded that the model based on GCSF (IBGC) was preferable to that from LIF (Sumikawa et al., FEBS Lett., 404, 234 (1997)). We evaluated the quality of this model (IBGC) by comparing with X-ray (Somers et al., EMBO., 16, 989 (1997)) and NMR (Xu et al., J. Mol. Biol., 268, 468 (1997)) structures. Consequently, normal mode calculations were carried out for this model, giving conformation fluctuations similar to the C alpha deviation pattern between X-ray and NMR structures.