Crystallographic refinement of interleukin 1 beta at 2.0 A resolution.

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Abstract
The structure of human recombinant interleukin 1.beta.(IL-1.beta.) has been refined by a restrained least-squares method to a crystallographic R factor of 17.2% to 2.0 .ALPHA.NG resolution. One-hundred sixty-eight solvent molcuels have been located, and isotropic temperature factors for each atom have been refined. The overall structure is composed of 12 .beta.-strands that can best be described as forming the four triangular faces of a tetrahedron with hydrogen bonding resembling normal antiparallel .beta.-sheets only at the vertices. The interior of this tetrahedron is filled by hydrophobic side chains. Analysis of sequence alignments with IL-1.beta. from other mammalian species shows the interior to be very well conserved with the exterior residues markedly less so. There does not appear to be a clustering of invariant amino acid side chains on the surface of the molecule, suggesting an area of interaction with the IL-1 receptor. Comparison of the IL-1.beta. structure with IL-1.alpha. sequences indicates that IL-1.alpha. probably has a similar overall folding as IL-1.beta. but binds to the receptor in a different fashion. The three-dimensional structure of the IL-1.beta. is analyzed in light of what has been suggested by previously published work on mutants and fragments of the molecule.