title: SecA localization and SecA-dependent secretion occurs at new division septa in group B Streptococcus.
abstract: Exported proteins of Streptococcus agalactiae (GBS), which include proteins localized to the bacterial surface or secreted into the extracellular environment, are key players for commensal and pathogenic interactions in the mammalian host. These proteins are transported across the cytoplasmic membrane via the general SecA secretory pathway and those containing the so-called LPXTG sorting motif are covalently attached to the peptidoglycan by sortase A. How SecA, sortase A, and LPXTG proteins are spatially distributed in GBS is not known. In the close relative Streptococcus pyogenes, it was shown that presence of the YSIRKG/S motif (literally YSIRKX3Gx2S) in the signal peptide (SP) constitutes the targeting information for secretion at the septum. Here, using conventional and deconvolution immunofluorescence analyses, we have studied in GBS strain NEM316 the localization of SecA, SrtA, and the secreted protein Bsp whose signal peptide contains a canonical YSIRKG/S motif (YSLRKykfGlaS). Replacing the SP of Bsp with four other SPs containing or not the YSIRKG/S motif did not alter the localized secretion of Bsp at the equatorial ring. Our results indicate that secretion and cell wall-anchoring machineries are localized at the division septum. Cell wall- anchored proteins displayed polar (PilB, Gbs0791), punctuate (CspA) or uniform distribution (Alp2) on the bacterial surface. De novo secretion of Gbs0791 following trypsin treatment indicates that it is secreted at the septum, then redistributed along the lateral sides, and finally accumulated to the poles. We conclude that the ±YSIRK SP rule driving compartimentalized secretion is not true in S. agalactiae.
authors.affiliation: Institut Pasteur, Unité de Biologie des Bactéries Pathogènes à Gram positif, Paris, France.
authors.forename: Sara
authors.initials: S
authors.lastname: Brega
authors.forename: Elise
authors.initials: E
authors.lastname: Caliot
authors.forename: Patrick
authors.initials: P
authors.lastname: Trieu-Cuot
authors.forename: Shaynoor
authors.initials: S
authors.lastname: Dramsi
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D016667:Bacterial Capsules / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D021382:Protein Sorting Signals; D021381:Protein Transport; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D013292:Streptococcus agalactiae / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; D000069816:SEC Translocation Channels; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins