National Center for
3URG: The Crystal Structure Of Anabaena Ccbp
Acta Crystallogr. Sect. F Struct. Biol. Cryst. Commun. (2012) 68 p.1409-1414
Obtaining crystals presented a bottleneck in the structural study of Anabaena cyanobacterial Ca(2+)-binding protein (CcbP). In this report, the promoting effect of Ellman's reagent [5,5'-dithiobis(2-nitrobenzoic acid); DTNB] on the crystallization of CcbP is described. CcbP contains one free cysteine. A quick and simple oxidation reaction with DTNB blocked the free cysteine in purified CcbP and generated a homogenous monomeric protein for crystallization. The crystal structure of DTNB-modified CcbP was determined by the single-wavelength anomalous diffraction method. Structure analysis indicated that DTNB modification facilitated crystallization of CcbP by inducing polar interactions in the crystal lattice. DTNB-mediated cysteine modification was demonstrated to have little effect on the overall structure and the Ca(2+) binding of CcbP. Thus, DTNB modification may provide a simple and general approach for protein modification to improve the success of crystallization screening.