title: Mechanism for sortase localization and the role of sortase localization in efficient pilus assembly in Enterococcus faecalis.
abstract: Pathogenic streptococci and enterococci primarily rely on the conserved secretory (Sec) pathway for the translocation and secretion of virulence factors out of the cell. Since many secreted virulence factors in gram-positive organisms are subsequently attached to the bacterial cell surface via sortase enzymes, we sought to investigate the spatial relationship between secretion and cell wall attachment in Enterococcus faecalis. We discovered that sortase A (SrtA) and sortase C (SrtC) are colocalized with SecA at single foci in the enterococcus. The SrtA-processed substrate aggregation substance accumulated in single foci when SrtA was deleted, implying a single site of secretion for these proteins. Furthermore, in the absence of the pilus-polymerizing SrtC, pilin subunits also accumulate in single foci. Proteins that localized to single foci in E. faecalis were found to share a positively charged domain flanking a transmembrane helix. Mutation or deletion of this domain in SrtC abolished both its retention at single foci and its function in efficient pilus assembly. We conclude that this positively charged domain can act as a localization retention signal for the focal compartmentalization of membrane proteins.
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, 660 S. Euclid Ave., Campus Box 8230, Saint Louis, MO 63110-1093, USA.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Kline
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Kau
authors.forename: Swaine L
authors.initials: SL
authors.lastname: Chen
authors.forename: Adeline
authors.initials: A
authors.lastname: Lim
authors.forename: Jerome S
authors.initials: JS
authors.lastname: Pinkner
authors.forename: Jason
authors.initials: J
authors.lastname: Rosch
authors.forename: Sreedhar R
authors.initials: SR
authors.lastname: Nallapareddy
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Murray
authors.forename: Birgitta
authors.initials: B
authors.lastname: Henriques-Normark
authors.forename: Wandy
authors.initials: W
authors.lastname: Beatty
authors.forename: Michael G
authors.initials: MG
authors.lastname: Caparon
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Hultgren
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D019881:Aminoacyltransferases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013293:Enterococcus faecalis / Q000201:enzymology* / Q000648:ultrastructure; D010861:Fimbriae, Bacterial / Q000378:metabolism* / Q000648:ultrastructure; D015151:Immunoblotting; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
chemical_list: D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; C509822:sortase C; D019881:Aminoacyltransferases; C120542:sortase A; D003546:Cysteine Endopeptidases; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins