Crystallization in cubo: general applicability to membrane proteins

Obtaining well ordered crystals of membrane proteins is the single most ser ious stumbling block in the pursuit of their high-resolution structures. Th e applicability of lipidic cubic phase-mediated crystallization is demonstr ated on a diverse set of bacterial membrane proteins: two photosynthetic re action centres, a light-harvesting complex and two retinal proteins, halorh odopsin and bacteriorhodopsin. Despite marked differences in molecular dime nsions, subunit composition and membrane origin, one single lipid, monoolei n, is sufficient to form a crystallization matrix for all the aforementione d systems. Therefore, the lipidic cubic phase approach is proposed as a gen eral method for crystallizing membrane proteins.