Antigenic polypeptide complex from the Melvin strain of Neisseria gonorrhoeae: isolation and properties

An antigenic complex has been isolated in a highly purified from from the Melvin strain of Neisseria gonorrhoeae. The complex has a molecular weight of 9.3 x 10(6) and on sodium dodecyl sulfate-polyacrylamide gel electrophoresis was found to consist of several subunits; the most predominant had the following molecular weights: 110,000, 94,000, 68,000, a smear containing (52,000, 48,000, and 44,000), 42,000, 36,000, 29,000, 28,000, 26,000, and 12,000 comprising 89% of the total protein. With the exception of the subunit of molecular weight 110,000, no change in the content or the mobility of other subunits was observed when beta-mercaptoethanol was omitted from the denaturation solution of sodium dodecyl sulfate electrophoresis. Amino acid analysis of the complex showed a predominance of hydrophobic amino acids. These data implicated noncovalent interactions between the subunits. When the cells were labeled with fluorescamine it was possible to obtain a fluorescent complex with identical properties. Among several buffers used for the isolation of the complex, 0.2 M tris(hydroxymethyl)aminomethane buffer (pH 7.5) gave maximum yield with low amounts of lipopolysaccharide and phospholipid; the choice of the buffer for column chromatography did not seem to make any difference. The high protein content and low amounts of lipopolysaccharide and phospholipid are characteristic properties of the complex.