Crystallization of OmpC osmoporin from Escherichia coli.

OmpC porin, one of the major outer-membrane proteins of Gram-negative bacteria, participates in bacterial osmoregulation by counteracting OmpF porin. Although these two osmoporins from Escherichia coli share high sequence homology, their crystallization behavior was found to be very different. OmpC could be crystallized under a variety of conditions by either microdialysis or hanging-drop methods using PEG 4000 as precipitant. The crystals belong to space group P21 with unit-cell constants a = 117.6, b = 110, c = 298.4 A, beta = 97 degrees. They diffract beyond 4 A with a rotating anode and show intense non-Bragg scattering.