Shigella flexneriis a Gram-negative, anaerobic bacterium in the genusShigellathat can cause diarrhoea in humans. SF173, a hypothetical protein fromS. flexneri5a strain M90T, has been cloned, overexpressed, purified and crystallized as a part of laboratory-scale structural genomics project. The SF173 protein was crystallized using the sitting-drop vapour-diffusion method in the presence of 0.8 Msuccinic acid pH 7.0 at 293 K. Preliminary X-ray diffraction analysis revealed that the crystal diffracted to 1.47 Å resolution and belonged to space groupI432, with unit-cell parametersa=b=c= 110.245 Å.