Crystallization of Integral Membrane Proteins

Abstract

Until 1980, it was considered quite unlikely that integral membrane proteins could be crystallized in three dimensions. In that year two groups (1,2) grew crystals of two different membrane proteins that yielded X-ray diffraction. With the refinements in the crystallization methods, several other groups have now reported crystals from seven membrane proteins (3,4,5,6,7,24), one of which has had its structure elucidated at high resolution (8). This rapid progress in the field of membrane protein structure analysis is not due to the use of radically new methods, but to the growing awareness and appreciation of the physical chemistry of detergent solubilized membrane proteins. In the short span of five years, much has been done but only short discussions have been published on the crystallization methods (9,10,11). We wish to review briefly the field as it stands and report on some previously unpublished observations from our group in Basel, particularly on the crystallization behavior of porin (Omp F), a pore-forming protein from the outer membrane of E. coli.