Crystallization and preliminary X-ray crystallographic studies on acyl-(acyl carrier protein) from Escherichia coli.

Acyl carrier proteins carry the lipid substrate to the enzymes of the fatty acid synthase system. Crystals of Escherichia coli acyl carrier protein to which a butyryl group has been attached via a thioester link to the phosphopantetheine prosthetic arm have been obtained by the hanging-drop vapour-diffusion method. These crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 27.6, b = 41.6, c = 63.7 A. The asymmetric unit appears to contain one subunit, corresponding to a packing density of 2.1 A(3) Da(-1). Crystals of the selenomethionine-substituted (SeMet) protein were obtained using different conditions and belong to space group P6(3), with unit-cell parameters a = b = 63.4, c = 37.0 A, alpha = beta = 90, gamma = 120 degrees and with a monomer in the asymmetric unit (V(M) = 2.5 A(3) Da(-1)). Crystals of a SeMet butyryl-ACP I62M variant were obtained using the conditions for the native protein. Like the native crystals, these belong to space group P2(1)2(1)2(1) and have unit-cell parameters a = 27.3, b = 41.9, c = 64.5 A. A data set suitable for MAD phasing was collected from the crystals of the I62M variant to 1.8 A resolution on the ESRF beamline ID14-4.