Abstract
Human interleukin-1 beta (IL-1 beta) is an important cytokine in the immune system which involves in inflammatory response, cell proliferation, differentiation and apoptosis, has been studied extensively. Five avian (chicken, duck, goose, turkey and pigeon) IL-1 betas share 31-35% protein sequence identity to mammal (human and murine) and are less well understood. In this study, we report the crystal structure of recombinant chicken IL-1 beta, to 1.58 angstrom resolution. The protein structure is comprised of 12 beta-strands and 1 alpha-helix, which form a barrel-shaped conformation. Modeling ligand docking of chicken IL-1 beta to its receptor reveals some differences at the site of interaction compared to human IL-1 beta. Molecular dynamics (MD) simulations reveal significant changes in the dynamic range of motion on receptor binding. The Loops 3 and 9 of chicken interleukin-1 beta have the most significant fluctuation before receptor binding. Upon binding, the flexibility of these loops, which are in direct contact with the receptor, markedly decreases. Taken together, these results suggest that receptor binding leads to not only favorable enthalpy but lower conformational entropy.