dTDP-4-dehydrorhamnose 3,5-epimerase is the third enzyme in the dTDP-L-rhamnose biosynthetic pathway, and catalyzes the conversion of dTDP-4-dehydro-6-deoxy-D-glucose to dTDP-4-dehydro-6-deoxy-L-mannose. This is an essential pathway in bacteria and is not present in humans. Therefore, it is considered a good target pathway for antimicrobial drug development. This protein is believed to form a complex with dTDP-4-dehydrorhamnose reductase, the fourth and final enzyme of the dTDP-L-rhamnose pathway. The crystal structure of the Bacillus anthracis epimerase was determined by molecular replacement and refined to 1.63 Å resolution. The protein is predominantly beta-stranded and has two domains: a short N-terminal oligomerization domain and larger C-terminal catalytic domain. Two molecules in the asymmetric unit form a dimer through extensive antiparallel hydrogen-bonding interactions of a beta strand from the oligomerization domain and a beta strand of the catalytic domain. One epimerase molecule has TDP and another PPi bound in the active site.