title: Secretome analysis of Anabaena sp. PCC 7120 and the involvement of the TolC-homologue HgdD in protein secretion.
abstract: Secretion of proteins is a central strategy of bacteria to influence and respond to their environment. Until now, there has been very few discoveries regarding the cyanobacterial secrotome or the secretion machineries involved. For a mutant of the outer membrane channel TolC-homologue HgdD of Anabaena sp. PCC 7120, a filamentous and heterocyst-forming cyanobacterium, an altered secretome profile was reported. To define the role of HgdD in protein secretion, we have developed a method to isolate extracellular proteins of Anabaena sp. PCC 7120 wild type and an hgdD loss-of-function mutant. We identified 51 proteins of which the majority is predicted to have an extracellular secretion signal, while few seem to be localized in the periplasmic space. Eight proteins were exclusively identified in the secretome of wild-type cells, which coincides with the distribution of type I secretion signal. We selected three candidates and generated hemagglutinin-tagged fusion proteins which could be exclusively detected in the extracellular protein fraction. However, these proteins are not secreted in the hgdD-mutant background, where they are rapidly degraded. This confirms a direct function of HgdD in protein secretion and points to the existence of a quality control mechanism at least for proteins secreted in an HgdD-dependent pathway.
authors.affiliation: Institute of Molecular Biosciences, Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9, Frankfurt/am Main, 60438, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Hahn
authors.forename: Mara
authors.initials: M
authors.lastname: Stevanovic
authors.forename: Eva
authors.initials: E
authors.lastname: Brouwer
authors.forename: Daniela
authors.initials: D
authors.lastname: Bublak
authors.forename: Joanna
authors.initials: J
authors.lastname: Tripp
authors.forename: Tobias
authors.initials: T
authors.lastname: Schorge
authors.forename: Michael
authors.initials: M
authors.lastname: Karas
authors.forename: Enrico
authors.initials: E
authors.lastname: Schleiff
mesh_terms: D017033:Anabaena / Q000235:genetics / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems / Q000235:genetics; D001692:Biological Transport / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D019897:Periplasm / Q000378:metabolism; D021381:Protein Transport
chemical_list: D001425:Bacterial Outer Membrane Proteins; D058947:Bacterial Secretion Systems; D026901:Membrane Transport Proteins