Involvement of a 40-kDa glycoprotein in food recognition, prey capture, and induction of phagocytosis in the protozoon Actinophrys sol.
A 40-kDa glycoprotein (gp40) was identified as a Con A-binding adhesive substance of the heliozoon Actinophrys sol for immobilizing and ingesting prey flagellates. Isolation and partial characterization of gp40 showed that: 1) gp40 is a major Con A-binding protein of Actinophrys with a molecular weight of 40 kDa, and is stored in secretory granules called extrusomes; 2) gp40 was purified by Con A-affinity chromatography, and the N-terminal amino acid sequence was determined as H2N-KVLK-FEDDFDTFDLQ; 3) prey flagellates became adhered to gp40-immobilized agarose beads; 4) phagocytosis of Actinophrys was induced against gp40-immobilized agarose beads; and 5) solubilized gp40 induced exocytosis of extrusomes and cell fusion of heliozoons. These results indicate that gp40 is a multi-functional secretory protein of Actinophrys, which is required in correct targeting of the heliozoon to food organisms as well as in self-recognition.
Sakaguchi
M
M
Department of Biology, Faculty of Science, Kobe University, Japan.
Murakami
H
H
Suzaki
T
T
D000595:Amino Acid Sequence; D000818:Animals; D002846:Chromatography, Affinity; D003208:Concanavalin A; D056890:Eukaryota / Q000502:physiology*; D006023:Glycoproteins / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry; D010587:Phagocytosis; D011235:Predatory Behavior; D015800:Protozoan Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D022142:Secretory Vesicles / Q000502:physiology
D006023:Glycoproteins; D010446:Peptide Fragments; D015800:Protozoan Proteins; D003208:Concanavalin A