EFFECTS OF ETHYLENEGLYCOL CHAIN-LENGTH OF DODECYL POLYETHYLENEGLYCOL MONOETHER ON THE CRYSTALLIZATION OF BOVINE HEART CYTOCHROME-C-OXIDASE

Tetragonal crystals that diffracted X-rays up to 5 Angstrom resolution were obtained from bovine heart cytochrome c oxidase isolated and solubilized with dodecyl octaethyleneglycol monoether, CH3(CH2)(11)O(CH2CH2O)(8)H. Comparison of observed structure factors between data sets each obtained from a different native crystal gave correlation coefficients of 0.92, 0.84 and 0.57 at 10 Angstrom, 7 Angstrom and 6 Angstrom resolution, respectively. The space group and the cell dimensions of the crystal are I4(1) or I4(3) and a = b = 253 Angstrom, c = 507 Angstrom, respectively The perfection and stability of the tetragonal crystals are significantly higher than those of the hexagonal crystals of the protein stabilized with Brij-35, CH3(CH2)(11)O(CH2CH2O)(23)H (whose details are reported elsewhere). Examination of the effect of ethyleneglycol chain length on the crystallization revealed that only dodecyl polyethyleneglycol monoethers with eight and seven units were appropriate for producing this type of crystal, indicating an optimum size of the detergent for crystallization of the membrane protein.