title: A Salmonella typhimurium effector protein SifA is modified by host cell prenylation and S-acylation machinery.
abstract: SifA is a Salmonella effector protein that is required for maintenance of the vacuolar membrane that surrounds replicating bacteria. It associates with the Salmonella-containing vacuole but how it interacts with the membrane is unknown. Here we show by immunofluorescence, S100 fractionation and Triton X-114 partitioning that the membrane association and targeting properties of SifA are influenced by a motif encoded within the C-terminal six amino acids. This sequence shares homology with both CAAX and Rab geranylgeranyl transferase prenylation motifs. We characterized the post-translational processing of SifA and showed that the cysteine residue within the CAAX motif is modified by isoprenoid addition through the action of protein geranylgeranyl transferase I. SifA was additionally modified by S-acylation of an adjacent cysteine residue. Similar modifications to host cell proteins regulate numerous functions including protein targeting, membrane association, protein-protein interaction, and signal transduction. This is the only known example of a bacterial effector protein that is modified both by mammalian cell S-acylation and prenylation machinery.
authors.affiliation: Division of Immunology, Department of Pathology, Center for Veterinary Science, University of Cambridge, United Kingdom.
authors.forename: Anna T
authors.initials: AT
authors.lastname: Reinicke
authors.forename: James L
authors.initials: JL
authors.lastname: Hutchinson
authors.forename: Anthony I
authors.initials: AI
authors.lastname: Magee
authors.forename: Piero
authors.initials: P
authors.lastname: Mastroeni
authors.forename: John
authors.initials: J
authors.lastname: Trowsdale
authors.forename: Adrian P
authors.initials: AP
authors.lastname: Kelly
mesh_terms: D000215:Acylation; D019883:Alkyl and Aryl Transferases / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology*; D002254:Carbonates / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry; D003600:Cytosol / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000737:chemistry / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017830:Octoxynol; D009841:Oligonucleotides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011092:Polyethylene Glycols / Q000494:pharmacology; D014176:Protein Biosynthesis; D012486:Salmonella typhimurium / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions; D013997:Time Factors; D014162:Transfection
chemical_list: D001426:Bacterial Proteins; D002254:Carbonates; D003902:Detergents; D006023:Glycoproteins; D009841:Oligonucleotides; C421862:SifA protein, Salmonella; D049452:Green Fluorescent Proteins; D011092:Polyethylene Glycols; C005686:sodium carbonate; D017830:Octoxynol; C010615:Nonidet P-40; D019883:Alkyl and Aryl Transferases; C083291:geranylgeranyltransferase type-I; D003545:Cysteine