Hoffmann A, Neumann P, Schierhorn A, Stubbs MT
Crystallization of Spätzle, a cystine-knot protein involved in embryonic development and innate immunity in Drosophila melanogaster. [Journal Article, Research Support, Non-U.S. Gov't]
Acta Crystallogr Sect F Struct Biol Cryst Commun 2008 Aug 1; 64(Pt 8):707-10.
The Spätzle protein is involved in both the definition of the dorsal-ventral axis during embryonic development and in the adult innate immune response. The disulfide-linked dimeric cystine-knot protein has been expressed as a proprotein in inclusion bodies in Escherichia coli and refolded in vitro by rapid dilution. Initial orthorhombic crystals that diffracted to 7 A resolution were obtained after three months by the sitting-drop vapour-diffusion method. Optimization of the crystallization conditions resulted in orthorhombic crystals (space group P2(1)2(1)2(1), with unit-cell parameters a = 53.0, b = 59.2, c = 62.5 A) that diffracted to 2.8 A resolution in-house. The small volume of the asymmetric unit indicated that it was not possible for the crystals to contain the complete pro-Spätzle dimer. Mass spectrometry, N-terminal sequencing and Western-blot analysis revealed that the crystals contained the C-terminal disulfide-linked cystine-knot dimer. Comparison of various crystallization experiments indicated that degradation of the N-terminal prodomain was dependent on the buffer conditions.
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