Paetzel M, Chernaia M, Strynadka N, Tschantz W, Cao G, Dalbey R E, James M N
Department of Chemistry, Ohio State University, Columbus 43210, USA.
Proteins. 1995 Sep;23(1):122-5. doi: 10.1002/prot.340230115.
Leader peptidase, a novel serine protease in Escherichia coli, catalyzes the cleavage of the amino-terminal leader sequences from exported proteins. It is an integral membrane protein containing two transmembrane segments with its carboxy-terminal catalytic domain residing in the periplasmic space. Here, we report a procedure for the purification and the crystallization of a soluble non-membrane-bound form of leader peptidase (delta 2-75). Crystals were obtained by the sitting-drop vapor diffusion technique using ammonium dihydrogen phosphate as the precipitant. Interestingly, we have found that the presence of the detergent Triton X-100 is required to obtain crystals sufficiently large for X-ray analysis. The crystals belong to the tetragonal space group P4(2)2(1)2, with unit cell dimensions of a = b = 115 A and c = 100 A, and contain 2 molecules per asymmetric unit. This is the first report of the crystallization of a leader (or signal) peptidase.
