Crystallization and preliminary X-ray analysis of human plasma apolipoprotein C-I.

Human apolipoprotein C-I, the smallest of the plasma apolipoproteins, is a component of several classes of plasma lipoproteins. Two crystalline forms of this protein, both suitable for high resolution X-ray diffraction analysis, have been obtained from mixtures of 2-methyl-2,4-pentanediol, sodium acetate, and octyl-beta-D-1-thioglucopyranoside at room temperature. The first form belongs to space group P2(1), with beta = 106 degrees and cell dimensions of a = 38.1 A, b = 50.8 A and c = 34.9 A. The asymmetric unit appears to contain two molecules of the protein. The second form belongs to space group P2(1)2(1)2(1), with cell dimensions of a = 34.5 A, b = 53.1 A, c = 71.1 A and it also appears to contain two molecules of the protein in the asymmetric unit.