Crystallization and preliminary X‐ray analysis of a 1:1 complex between a designed monomeric interferon‐gamma and its soluble receptor

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Abstract
A variant of human interferon-gamma (IFN-γ) has been created in which the two chains of the homodimeric cytokine were linked N- to C-terminus by an eight residue polypeptide linker. The sequence of this linker was derived from a loop in bira bifunctional protein, and was determined from a structural database search. This “single-chain” variant was used to create an IFN-γ molecule that binds only a single copy of the α-chain receptor, rather than the 2 α-chain receptor: 1 IFN-γ binding stoichiometry observed for the native hormone. Crystals have been grown of a 1:1 complex between this single-chain molecule and the extracellular domain of its α-chain receptor. These crystals diffract beyond 2.0 Å, significantly better than the 2.9 Å observed for the native 2:1 complex. Density calculations suggest these crystals contain two complexes in the asymmetric unit; a self-rotation function confirms this conclusion.
Funding Information
  • NIH (GM08388)