title: Excretion of cytoplasmic proteins (ECP) in Staphylococcus aureus.
abstract: Excretion of cytoplasmic proteins (ECP) is a common physiological feature in bacteria and eukaryotes. However, how these proteins without a typical signal peptide are excreted in bacteria is poorly understood. We studied the excretion pattern of cytoplasmic proteins using two glycolytic model enzymes, aldolase and enolase, and show that their excretion takes place mainly during the exponential growth phase in Staphylococcus aureus very similar to that of Sbi, an IgG-binding protein, which is secreted via the Sec-pathway. The amount of excreted enolase is substantial and is comparable with that of Sbi. For localization of the exit site, we fused aldolase and enolase with the peptidoglycan-binding motif, LysM, to trap the enzymes at the cell wall. With both immune fluorescence labeling and immunogold localization on electron microscopic thin sections aldolase and enolase were found apart from the cytoplasmic area particularly in the cross wall and at the septal cleft of dividing cells, whereas the non-excreted Ndh2, a soluble NADH:quinone oxidoreductase, is only seen attached to the inner side of the cytoplasmic membrane. The selectivity, the timing and the localization suggest that ECP is not a result of unspecific cell lysis but is mediated by an as yet unknown mechanism.
authors.affiliation: Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Ebner
authors.affiliation: Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Prax
authors.affiliation: Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.
authors.forename: Mulugeta
authors.initials: M
authors.lastname: Nega
authors.affiliation: Max Planck Institute for Developmental Biology, Spemannstr. 35, 72076, Tübingen, Germany.
authors.forename: Iris
authors.initials: I
authors.lastname: Koch
authors.affiliation: Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.
authors.forename: Linda
authors.initials: L
authors.lastname: Dube
authors.affiliation: Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.
authors.forename: Wenqi
authors.initials: W
authors.lastname: Yu
authors.affiliation: Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.
authors.forename: Janina
authors.initials: J
authors.lastname: Rinker
authors.affiliation: Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Popella
authors.affiliation: Max Planck Institute for Developmental Biology, Spemannstr. 35, 72076, Tübingen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Flötenmeyer
authors.affiliation: Microbial Genetics, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Götz
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D005634:Fructose-Bisphosphate Aldolase / Q000378:metabolism; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D011485:Protein Binding; D013211:Staphylococcus aureus / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D005634:Fructose-Bisphosphate Aldolase; D010751:Phosphopyruvate Hydratase