title: Translocation of an 89-kDa periplasmic protein is associated with Holospora infection.
abstract: The symbiotic bacterium Holospora obtusa infects the macronucleus of the ciliate Paramecium caudatum. After ingestion by its host, an infectious form of Holospora with an electron-translucent tip passes through the host digestive vacuole and penetrates the macronuclear envelope with this tip. To investigate the underlying molecular mechanism of this process, we raised a monoclonal antibody against the tip-specific 89-kDa protein, sequenced this partially, and identified the corresponding complete gene. The deduced protein sequence carries two actin-binding motifs. Indirect immunofluorescence microscopy shows that during escape from the host digestive vacuole, the 89-kDa proteins translocates from the inside to the outside of the tip. When the bacterium invades the macronucleus, the 89-kDa protein is left behind at the entry point of the nuclear envelope. Transmission electron microscopy shows the formation of fine fibrous structures that co-localize with the antibody-labeled regions of the bacterium. Our findings suggest that the 89-kDa protein plays a role in Holospora's escape from the host digestive vacuole, the migration through the host cytoplasm, and the invasion into the macronucleus.
authors.affiliation: Biological Institute, Faculty of Science, Yamaguchi University, Yoshida 1677-1, Yamaguchi 753-8512, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Iwatani
authors.forename: Hideo
authors.initials: H
authors.lastname: Dohra
authors.forename: B Franz
authors.initials: BF
authors.lastname: Lang
authors.forename: Gertraud
authors.initials: G
authors.lastname: Burger
authors.forename: Manabu
authors.initials: M
authors.lastname: Hori
authors.forename: Masahiro
authors.initials: M
authors.lastname: Fujishima
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D001483:Base Sequence; D049109:Cell Proliferation; D015180:Electrophoresis, Gel, Two-Dimensional; D042281:Holosporaceae / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010247:Paramecium / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D033903:Periplasmic Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D000906:Antibodies; D033903:Periplasmic Proteins