The porin (PorB) of Neisseria gonorrhoeae has been implicated in the pathog
enesis of this species. Porin is believed to translocate from the bacterial
outer membrane into target cell membranes affecting various cell functions
. Here we investigated the effect of porin on phagosome maturation. Phagocy
tosis of latex beads by human macrophages was allowed in the presence or ab
sence of purified porin. Isolation of latex bead-containing phagosomes and
subsequent two-dimensional gel electrophoresis revealed substantial differe
nces in the phagosomal protein composition. Immunoblotting detected higher
amounts of annexin II and the early endocytic markers Rab5 and transferrin
receptor and decreased levels of the late endocytic markers Rab7 and cathep
sin D in phagosomes obtained in the presence of porin compared with those o
btained in its absence. Furthermore, association of Rab4 with the latex bea
d-containing phagosomes was revealed by flow cytometry. The amount of this
small GTPase was markedly higher in the phagosomes isolated in the presence
of porin. The data thus indicate that neisserial porin is itself able to a
rrest phagosome maturation within macrophages.