title: Protein A is released into the Staphylococcus aureus culture supernatant with an unprocessed sorting signal.
abstract: The immunoglobulin binding protein A (SpA) of Staphylococcus aureus is synthesized as a precursor with a C-terminal sorting signal. The sortase A enzyme mediates covalent attachment to peptidoglycan so that SpA is displayed on the surface of the bacterium. Protein A is also found in the extracellular medium, but the processes involved in its release are not fully understood. Here, we show that a portion of SpA is released into the supernatant with an intact sorting signal, indicating that it has not been processed by sortase A. Release of SpA was reduced when the native sorting signal of SpA was replaced with the corresponding region of another sortase-anchored protein (SdrE). Similarly, a reporter protein fused to the sorting signal of SpA was released to a greater extent than the same polypeptide fused to the SdrE sorting signal. Released SpA protected bacteria from killing in human blood, indicating that it contributes to immune evasion.
authors: Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland.
authors: Dara P
authors: DP
authors: O'Halloran
authors: Proteomics Core Facility, Conway Institute, University College Dublin, Dublin, Ireland.
authors: Kieran
authors: K
authors: Wynne
authors: Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin, Ireland geoghegj@tcd.ie.
authors: Joan A
authors: JA
authors: Geoghegan
mesh_terms: D019881:Aminoacyltransferases / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D002473:Cell Wall / Q000276:immunology*; D003546:Cysteine Endopeptidases / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D010450:Endopeptidases / Q000378:metabolism; D006801:Humans; D057131:Immune Evasion / Q000276:immunology*; D010457:Peptidoglycan / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013203:Staphylococcal Infections / Q000276:immunology / Q000382:microbiology; D013205:Staphylococcal Protein A / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D013211:Staphylococcus aureus / Q000276:immunology* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D010457:Peptidoglycan; D011993:Recombinant Fusion Proteins; C118507:SdrE protein, Staphylococcus aureus; D013205:Staphylococcal Protein A; D019881:Aminoacyltransferases; C120542:sortase A; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; C120985:LytM protein, Staphylococcus aureus
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