THE SERINE-RICH ENTAMOEBA-HISTOLYTICA PROTEIN IS A PHOSPHORYLATED MEMBRANE-PROTEIN CONTAINING O-LINKED TERMINAL N-ACETYLGLUCOSAMINE RESIDUES

Previously, we described the isolation of a cDNA clone and the gene en coding a protective antigen of the protozoan parasite Entamoeba histol ytica, the serine-rich Entamoeba histolytica protein (SREHP). The deri ved amino acid sequence of the SREHP cDNA clone was remarkable for a h igh serine content (52/233 amino acids), a putative signal sequence, m ultiple hydrophilic dodecapeptide and octapeptide tandem repeats, and a hydrophobic C-terminal putative membrane-spanning region. Here, we s how that SREHP is modified by the addition of phosphate at serine resi dues, O-linked terminal N-acetylglucosamine residues, and by acylation . When the SREHP gene is expressed in baculovirus transformed Sf-9 cel ls, the product is also phosphorylated and glycosylated and is localiz ed to the plasma membrane of the insect cells, The native SREHP molecu le also serves as a potent chemoattractant for amebic trophozoites. Th e data presented here suggest that SREHP is a unique membrane protein with phosphorylation and glycosylation patterns usually associated wit h nuclear or cytoplasmic proteins.