The crystallization of outer membrane proteins from Escherichia coli. Studies on lamB and ompA gene products

The outer membrane protein LambB from Escherichia coli has been crystallized from detergent-containing solutions. Several different crystal habits can be obtained under the same ionic and precipitant conditions by altering the detergent head group composition of the protein-detergent mixed micelle or by adding polar organic compounds. Two crystal forms have been partially characterized as P1 and C2221, the former diffracting to beyond 4 A resolution and the latter to 6 A. The detergents used were beta-octyl glucoside, octyl tetraoxyethylene, and octyl polyoxyethylene (polydisperse) either alone or as mixtures. In some experiments, the addition of small nonionic amphiphiles having n-butyl alkyl tails significantly influenced crystallization. The experiments suggest that the detergent region of the mixed micelle plays a critical role in crystal formation. Using the methods developed here for LamB and also for matrix porin (Garavito, R. M., Jenkins, J. A., Jansonius, J. N., Karlsson, R., and Rosenbusch, J. P. (1983) J. Mol. Biol. 164, 313-327), an additional protein from the outer membrane, OmpA, has been obtained as a microcrystalline preparation.