THE CAMPYLOBACTER-JEJUNI PORIN TRIMERS PACK INTO DIFFERENT LATTICE TYPES WHEN RECONSTITUTED IN THE PRESENCE OF LIPID

Purified major outer membrane protein of Campylobacter jejuni exhibite d different classes of molecules by SDS/PAGE and immunoblotting. A hig h-molecular-mass product (120-140 kDa) was observed under mild conditi ons of solubilization, a folded monomeric form of 35 kDa was seen when treated at high SDS concentrations and finally, a single band around 45 kDa occurred when the sample was heated to 96 degrees C [Bolla, J. M., Loret, E., Zalewski, M. & Pages, J. M. (1995) J. Bacteriol. 177, 4 266-4271]. The high-molecular-mass product was reconstituted into two- dimensional crystals in the presence of phospholipids and Mg2+. The C. jejuni porin required different conditions for successful reconstitut ion into two-dimensional crystals than the Escherichia coli porin OmpF . Electron microscopy and digital image processing of negatively stain ed specimens revealed a rectangular lattice with a unit cells size of a = 8.9 nm, b = 14.9 nm, an oblique lattice with a = 8.9 nm, b = 30.1 nm, gamma = 98 degrees, and a trigonal lattice with a = b = 9.6 nm. Pr ojection maps were calculated to a resolution of 2 nm, and exhibited a trimeric protein with three stain-filled indentations.