Association of host proteins with the broad host range filamentous phage Ngoφ6 ofNeisseria gonorrhoeae

AllNeisseria gonorrhoeaestrains contain multiple copies of integrated filamentous phage genomes with undefined structures. In this study, we sought to characterize the capsid proteins of filamentousN.gonorrhoeaebacteriophage Ngo phi 6 and phagemids propagated in different bacteria. The data demonstrate that purified phage contain phage-encoded structural proteins and bacterial host proteins; host proteins consistently copurified with the phage particles. The bacterial host proteins associated with the phage filament (as identified by mass spectrometry) tended to be one of the predominant outer membrane components of the host strain, plus minor additional host proteins. We were able to copurify a functional ss-lactamase, a phagemid-encoded protein, with phage filaments. We used protein modeling and immunological analysis to identify the major phage encoded structural proteins. The antigenic properties of these proteins depended on the bacterium where the phages were propagated. Polyclonal antibodies againstN.gonorrhoeaephage Ngo phi 6 recognized phage-encoded proteins if the phage was propagated inN.gonorrhoeaeorH.influenzaecells but not if it was propagated inSalmonellaorE.coli. We show that the phage filaments isolated from gonococci andHaemophilusare glycosylated, and this may explain the antigenic diversity seen. Taken en toto, the data demonstrate that while the neisserial filamentous phage are similar to otherInoviruswith respect to overall genomic organization, their ability to closely associate with host proteins suggests that they have unique surface properties and are secreted by a here-to-fore unknown secretory pathway.