Biochemical, immunological and ultrastructural characterization of aggregation substances encoded by Enterococcus faecalis sex-pheromone plasmids.
The sex-pheromone system of Enterococcus faecalis can be viewed as a unique and highly efficient plasmid-collection mechanism. The contact needed for transfer of the conjugative sex-pheromone plasmids is mediated by an adhesin, called aggregation substance, which is encoded by these plasmids. We show here that for 17 of the 18 sex-pheromone plasmids (pAM373 being the exception) described to date, their adhesins are immunologically related to each other. In each case, we observed the presence of an N-terminal fragment of about 78 kDa in addition to the 137-kDa form of mature aggregation substance. The cross-reactions were different for the various plasmids. In the case of pPD1 the 78-kDa fragment reacted only weakly. The aggregation substance encoded by sex-pheromone plasmid pAD1 (Asa1) was characterized in detail. The conditions used for SDS/PAGE had a drastic influence on the migration behavior of mature aggregation substance and differently migrating, interconvertible forms were identified. Preliminary data indicate that Asa1 might be a glycoprotein. Antibodies were isolated which are directed against the N- and C-terminal parts of aggregation substance. They showed about the same reactivity on Western blots; however, only antibodies directed against the N-terminal part of the aggregation substance could inhibit the bacterial cell/cell contact. The reactions of the two antibody preparations with induced cells of E. faecalis was analyzed by transmission electron microscopy. The results indicated that especially the N-terminal part of aggregation substance is exposed on the cell surface of E. faecalis; the C-terminal part seems to be much less exposed.
Hirt
H
H
Lehrstuhl für Mikrobiologie, Universität München, Federal Republic of Germany.
Wanner
G
G
Galli
D
D
Wirth
R
R
D000906:Antibodies; D000941:Antigens / Q000276:immunology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D013293:Enterococcus faecalis / Q000737:chemistry* / Q000235:genetics; D008854:Microscopy, Electron; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D010957:Plasmids; D012724:Sex Attractants / Q000737:chemistry* / Q000235:genetics / Q000276:immunology
D000906:Antibodies; D000941:Antigens; D001426:Bacterial Proteins; D010446:Peptide Fragments; D012724:Sex Attractants; C065937:aggregation substance, Enterococcus faecalis