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 sol ubilized with dodecyl octaethyleneglycol monoether, CH3(CH2)(11)O(CH2C H2O)(8)H. Comparison of observed structure factors between data sets e ach obtained from a different native crystal gave correlation coeffici ents 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 t he crystal are I4(1) or I4(3) and a = b = 253 Angstrom, c = 507 Angstr om, respectively The perfection and stability of the tetragonal crysta ls are significantly higher than those of the hexagonal crystals of th e protein stabilized with Brij-35, CH3(CH2)(11)O(CH2CH2O)(23)H (whose details are reported elsewhere). Examination of the effect of ethylene glycol chain length on the crystallization revealed that only dodecyl polyethyleneglycol monoethers with eight and seven units were appropri ate for producing this type of crystal, indicating an optimum size of the detergent for crystallization of the membrane protein.