Crystal structure of core streptavidin determined from multiwavelength anomalous diffraction of synchrotron radiation.

A three-dimensional crystal structure of the biotin-binding core of streptavidin has been determined at 3.1-A resolution. The structure was analyzed from diffraction data measured at three wavelengths from a single crystal of the selenobiotinyl complex with streptavidin. Streptavidin is a tetramer with subunits arrayed in D2 symmetry. Each protomer is an 8-stranded beta-barrel with simple up-down topology. Biotin molecules are bound at one end of each barrel. This study demonstrates the effectiveness of multiwavelength anomalous diffraction (MAD) procedures for macromolecular crystallography and provides a basis for detailed study of biotin-avidin interactions.