Separation of the outer membrane and identification of major outer membrane proteins from Porphyromonas gingivalis.

The outer membrane of Porphyromonas gingivalis, an oral strict anaerobe, was isolated by sucrose density gradient centrifugation. The outer membrane obtained by the differential detergent extraction method, previously reported, showed an essentially similar protein pattern on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), confirming that the latter method is suitable for the study of outer membrane proteins in this organism. N-terminal amino acid sequence analysis revealed that major outer membrane proteins in this organism included Arg-gingipain, Lys-gingipain, RagA (a TonB-linked receptor), and putative porins that were homologous to Escherichia coli OmpA.