High-molecular-weight antigenic protein complex in the outer membrane of Neisseria gonorrhoeae

Abstract

The outer membrane of Neisseria gonorrhoeae contains approximately 15 proteins, with 2 or 3 accounting for over 75% of the total protein mass. Samples of outer membrane from strain 2686 T4 analyzed by electrophoresis in 2% polyacrylamide gels revealed a band with an apparent molecular weight of 800,000. The band was protein material, as indicated by trypsin and pronase sensitivity and by L-[3H]proline incorporation. Peptidoglycan, nucleic acids, and carbohydrate were not detected in the band. Dye binding, L-[3H]proline incorporation, and labeling of solubilized outer-membrane proteins with 125I-labeled Bolton-Hunter reagent indicated that the band made up 10 to 13% of the total protein mass of isolated outer membranes. The material in the band was purified by gel filtration and, after reduction and alkylation, quantitatively recovered as subunits with an apparent molecular weight of 76,000. The protein in complex form was exposed at the cell surface, as evidenced by labeling whole cells with 125I by using a lactoperoxidase-catalyzed reaction and with CNBr-activated dextran. Rabbit serum raised against whole 2686 T4 gonococci contained antibody which reacted with the protein complex. The protein complex was detected in all gonococcal strains tested, but its presence could not be demonstrated in several other gram-negative species.