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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.
Insights
Neisseria gonorrhoeae outer membranes contain a major protein complex. This complex, comprising 10-13% of total protein, is exposed on the cell surface and is specific to gonococci.
Area of Science:
- Microbiology
- Structural Biology
- Bacterial Pathogenesis
Background:
- The outer membrane of Neisseria gonorrhoeae is crucial for bacterial structure and interaction with the host.
- It comprises approximately 15 proteins, with a few dominating the protein mass.
Purpose of the Study:
- To characterize a prominent protein complex identified in the Neisseria gonorrhoeae outer membrane.
- To determine its abundance, molecular weight, and surface exposure.
Main Methods:
- Electrophoresis and gel filtration for protein purification and molecular weight determination.
- Enzymatic (trypsin, pronase) and radiolabeling (L-[3H]proline, 125I) techniques to confirm protein nature and surface localization.
- Immunological assays (rabbit antiserum) to detect specific antibodies against the complex.
Main Results:
- A high molecular weight (800,000) protein complex was identified in the outer membrane of Neisseria gonorrhoeae strain 2686 T4.
- This complex constituted 10-13% of the total outer membrane protein mass.
- The complex was confirmed as proteinaceous, exposed on the cell surface, and composed of 76,000 molecular weight subunits after reduction.
- Antibodies against whole gonococci recognized this complex, which was present in all tested gonococcal strains but not in other Gram-negative species.
Conclusions:
- Neisseria gonorrhoeae possesses a major, surface-exposed outer membrane protein complex unique to the species.
- This protein complex represents a significant structural component and potential target for immunological investigation.