Crystallization of peptidase T from Salmonella typhimurium.

Aminotripeptidase (peptidase T) from Salmonella typhimurium and a derivative carrying a C-terminal His tag have been crystallized. In both cases, the space group was found to be C2, with a single molecule in the asymmetric unit. Crystals of the native peptidase T diffract to 2.9 A, but a selenomethionine derivative of this protein did not yield good crystals. Crystals of the His-tag peptidase T diffracted to 2.6 A, however, and could be used for the production of good-quality selenomethionine crystals. All 15 methionines, a native metal ion and two mercury reactive sites could be located and crystals suitable for MAD data collection have been produced.