Immunobiological activities of a porin fraction isolated from Fusobacterium nucleatum ATCC 10953

Abstract

From Fusobacterium nucleatum ATCC 10953 cell envelope fraction whose inner membranes had been removed by treatment with sodium N-lauroyl sarcosinate, an outer membrane protein (37,000 Mr in a native state) was prepared by extraction with lithium dodecyl sulfate. The protein thus obtained showed distinct porin activity, namely, the ability to form hydrophilic diffusion pores by incorporation into the artificial liposome membrane. The porin fraction exhibited strong immunobiological activities in the in vitro assays: B-cell mitogenicity and polyclonal B-cell activation on murine splenocytes, stimulatory effects on guinea pig peritoneal macrophages, and enhancement of the migration of human blood monocytes. The porin fraction also exhibited immunoadjuvant activity to increase the antibody production against sheep erythrocytes in the spleen of mice that were immunized by sheep erythrocytes with porin. Although chemical analyses revealed that the test porin fraction contained a considerable amount of lipopolysaccharide (LPS) (around 12% of the fraction), the studies with LPS-nonresponding C3H/HeJ mice and on the inhibitory effects of polymyxin B strongly suggest that most of the above bioactivities are due to porin protein itself, not to coexistent LPS in the porin fraction.

The Fusobacterium nucleatum Major Outer‐Membrane Protein (FomA) Forms Trimeric, Water‐Filled Channels in Lipid Bilayer Membranes

“…The invasiveness of F: nucleaturn is thought to be initiated by coaggregation with Strep-tococcuS sunguis. The fusobacterial major outer-membrane protein, encoded by the fomA gene and therefore termed FomA (fusobacterial outer-membrane protein A) [ 51, has been proposed to participate in the binding of S. sanguis 161 and to exhibit immunobiological activities [7]. This protein has previously been isolated from different strains and characterized [S].…”

“…The primary structure showed no sequence homology with other known porins [ S ] , but by applying the principles recognized for the porins in Eschericlzia coli, a topology model was proposed for the FoniA protein, indicating a strong structural resemblance with the porin from Rhodnbacter cuinulutus as well as OmpF (matrix porin) and PhoE (phosphoporin) from E. coli 19,101. Furthermore, Takada et al [7] reported some porin activity of a fraction presumably containing the FomA protein from F: nucleatum ATCC 10953 by the liposome swelling method. These studies strongly suggested that FomA can exhibit porin properties.…”

Growth conditions and outer membrane proteins of Fusobacterium nucleatum

“…So far, very little has been published on the function ofthe various outer membrane proteins of F. nucieatum. (17)(18)(19). We have found (4) that some strains, before transition to stationary phase growth, had depleted the pool of some amino acids in the medium, in particular gltitamate and aspartate, and had started to take up peptides containing the same amino acids.…”

Molecular cloning and characterization of the genes encoding the immunoreactive major cell-surface proteins of Porphyromonas gingivalis

“…have been extensively studied in terms of purification [3], biochemical characterization [3,4], gene cloning of the subunit protein (fimbrilin) [5] and their immunobiological activities [6][7][8]. Nevertheless, there are only a few reports on the chemical structures and bioactivities of the cell-surface proteins of periodontitis-associated bacteria [9,10]. In the present study, we report on purification of the major cell-surface proteins of P. gingivalis, molecular cloning and sequencing of the corresponding genes, and examination of the antibodies reactive with the protein in serum specimens of patients with adult periodontitis compared with those of the fimbriae.…”