X-ray structural studies of the cytokine interleukin 1-beta.

The structure of the human cytokine, interleukin 1-beta (IL1-beta) is composed almost wholly of anti-parallel beta-sheet, organized in a three-fold repeating motif. The beta strands comprising the protein core are interconnected by 11 surface loops that form prominent features on the surface of the molecule. Comparisons of the amino acid sequences of different species of IL1-beta and the related cytokine IL1-alpha show that the majority of conserved residues form the structural core of the molecule, and that most variability occurs in the termini and surface loops that presumably bind the IL1 receptor. These results suggest that there may be some degree of flexibility in interactions made between IL1 and its cell surface receptor.