Structural change and receptor binding in a chemokine mutant with a rearranged disulfide: X-ray structure of e38C/C50A IL-8 at 2 Å resolution

The characteristic CXC chemokine disulfide core of interleukin-8 (IL-8) has been rearranged in a variant replacing the 9-50 disulfide with a 9-38 disulfide. The new variant has been characterized by its binding affinity to IL-8 receptors A and B and the erythrocyte receptor DARC. This variant binds the three receptors with affinities between 500- and 2,500-fold lower than wild-type IL-8. Binding affinity results are also reported for the variant with alanine substituted for both cysteines 9 and 50. The Glu38-->Cys/Cys50-->Ala IL-8 crystallizes in space group P2(1)2(1)2(1) with cell parameters a = 46.4, b = 49.2, and c = 69.5 A, and has been refined to an R-value of 19.4% for data from 10 to 2 A resolution. Analysis of the structure confirms the new disulfide arrangement and suggests that changes at Ile10 may be the principal cause of the lowered affinities.