title: Functional glycosylphosphatidylinositol anchor signal sequences in the Pneumocystis carinii PRT1 protease family.
abstract: Pneumocystis carinii is fungus which is a frequent cause of severe pneumonia in immunocompromised individuals. The P. carinii genome contains the PRT1 subtelomeric multigene family that encodes a kexin-like serine protease which is expressed on the surface of P. carinii. Analysis of the sequence of the carboxy-terminal sequence of many copies of PRT1 showed that they contained motifs characteristic of a glycosylphosphatidylinositol (GPI) anchor signal sequence. The ability of the C-terminal sequences of PRT1 to direct the addition of a GPI anchor was tested. CD14, a GPI-anchored monocyte glycoprotein antigen, was used as the basis of a heterologous system. CD14 was truncated to remove the carboxy-terminal sequences responsible for GPI-anchor addition. Addition of carboxy-terminal sequences from PRT1 restored high-level surface expression to the truncated CD14. Further, the majority of CD14-PRT1 recombinant protein was removed from the cell membrane by treatment with GPI-specific phospholipase C. These results suggest that the carboxy-terminal residues of most of the members of the PRT1 family of proteases have the potential to form a functional GPI-attachment signal.
authors.affiliation: Molecular Infectious Diseases Group, Department of Pediatrics, Institute of Molecular Medicine, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom.
authors.forename: R J
authors.initials: RJ
authors.lastname: Palmer
authors.forename: A E
authors.initials: AE
authors.lastname: Wakefield
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D039621:Eukaryotic Initiation Factor-3; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D018950:Lipopolysaccharide Receptors / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011010:Pneumocystis / Q000378:metabolism*; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D012697:Serine Endopeptidases / Q000235:genetics* / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D039621:Eukaryotic Initiation Factor-3; D005656:Fungal Proteins; D017261:Glycosylphosphatidylinositols; D018950:Lipopolysaccharide Receptors; D021382:Protein Sorting Signals; C050998:Prt1 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D010738:Type C Phospholipases; C442321:PRT1 serine protease; D012697:Serine Endopeptidases