Crystal structure of the cytokine interleukin‐1 beta

The crystal structure of human recombinant interleukin‐1 beta has been determined at 3.0 A resolution by the isomorphous replacement method in conjunction with solvent flattening techniques. The model prior to refinement has a crystallographic R‐factor of 42.3%. The structure is composed of 12 beta‐strands forming a complex network of hydrogen bonds. The core of the structure can best be described as a tetrahedron whose edges are each formed by two antiparallel beta‐strands. The interior of this structure is filled with hydrophobic side chains. There is a 3‐fold repeat in the folding of the polypeptide chain. Although this folding pattern suggests gene triplication, no strong internal sequence homology between topologically corresponding residues exists. The folding topology of interleukin‐1 beta is very similar to that described by McLachlan (1979) J. Mol. Biol., 133, 557‐563, for soybean trypsin inhibitor.