Crystallization and preliminary X-ray analysis of outer membrane phospholipase A from Escherichia coli

The outer membrane phospholipase A (OMPLA) of Escherichia coli is one of the few integral outer membrane proteins displaying enzymatic activity. It is encoded as a mature protein of 269 amino acids preceded by a signal sequence of 20 amino acids. There is no sequence homology with water-soluble lipases and phospholipases. Crystals of the mature enzyme were obtained at 22 degrees C from 24-28% (v/v) 2-methyl-2,4-pentanediol in Bis-Tris buffer, pH 5.9-6.0, with 1 mM calcium chloride and 1.5% (w/v) beta-octylglucoside. They have the symmetry of the trigonal spacegroup P3(1)21 (or P3(2)21) with cell dimensions of a = b = 79.6 A and c = 102.8 A (alpha = beta = 90 degrees, gamma = 120 degrees). Native crystals diffract to a resolution of 2.6 A.