1.9 A crystal structure of interleukin 6: implications for a novel mode of receptor dimerization and signaling.
Somers, W., Stahl, M., Seehra, J.S.(1997) EMBO J 16: 989-997
- PubMed: 9118960 
- DOI: https://doi.org/10.1093/emboj/16.5.989
- Primary Citation of Related Structures:  
1ALU - PubMed Abstract: 
Interleukin 6 (IL-6) has many biological activities in vivo, and deregulation has been implicated in many disease processes. IL-6, a 185 amino acid polypeptide was refolded, purified and crystallized. The crystals diffracted to beyond 1.9 A and the structure was solved using single isomorphous replacement. The X-ray structure of IL-6 is composed of a four helix bundle linked by loops and an additional mini-helix. 157 out of 185 residues are well defined in the final structure, with 18 N-terminal and 8 A-B loop amino acids displaying no interpretable electron density. The three-dimensional structure has been used to construct a model of IL-6 interacting with the IL-6 receptor (alpha-chain) and gp130 (beta-chain) that gives new insight into the process of molecular recognition and signaling. Based on this model, we predict a fourth binding site on IL-6, a low affinity IL-6-IL-6 interaction, which may be necessary for the sequential assembly of a functional hexameric IL-6 receptor complex.
Organizational Affiliation: 
Small Molecule Drug Discovery, Genetics Institute, Inc., Cambridge, MA 02140, USA.