125I-peptide mapping of protein III isolated from four strains of Neisseria gonorrhoeae.

Gonococcal outer-membrane protein I (PI) and PIII were isolated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis from reduced and unreduced whole-cell and outer-membrane lysates of four strains of nonpiliated (P-), transparent (O-) Neisseria gonorrhoeae. These proteins were radioiodinated and digested with alpha-chymotrypsin. The resultant 125I-peptides were then resolved by high-voltage thin-layer electrophoresis, followed by ascending thin-layer chromatography, and visualized by autoradiography. Results corroborated previous observations regarding the structural relationships of PIs having different apparent subunit molecular weights. All PIIIs had very similar apparent primary structures, regardless of the strain from which they were isolated, the source (i.e., whole cells or outer membranes), or the reduction state of the sodium dodecyl sulfate lysates. By the techniques used, it appeared that PIII is structurally similar in all of the gonococcal strains studied, even though each strain had structurally unique PIs.