Crystallization and preliminary X-ray analysis of a conserved hypothetical protein PAE2754 from Pyrobaculum aerophilum and of a double Leu-->Met mutant engineered for MAD phasing.

Structural genomics offers a potential route to the discovery of protein function. As part of a structural genomics project focused on the hyperthermophilic crenarchaeon Pyrobaculum aerophilum, a conserved hypothetical protein, PAE2754, has been expressed in Escherichia coli, purified and crystallized. Because of the difficulties of preparing interpretable heavy-atom derivatives with limited resolution and 8-12 molecules in the asymmetric unit, two leucine residues were selected for mutation to methionine. The double mutant L65M/L80M was created, expressed incorporating SeMet and crystallized. The crystals are monoclinic, space group P2(1), with unit-cell parameters a = 56.4, b = 193.3, c = 60.5 A, beta = 94.6 degrees and eight molecules (two tetramers) in the asymmetric unit. The crystals diffract to 2.75 A resolution and are suitable for MAD phasing.