title: Protein export through the bacterial Sec pathway.
abstract: The general secretory (Sec) pathway comprises an essential, ubiquitous and universal export machinery for most proteins that integrate into, or translocate through, the plasma membrane. Sec exportome polypeptides are synthesized as pre-proteins that have cleavable signal peptides fused to the exported mature domains. Recent advances have re-evaluated the interaction networks of pre-proteins with chaperones that are involved in pre-protein targeting from the ribosome to the SecYEG channel and have identified conformational signals as checkpoints for high-fidelity targeting and translocation. The recent structural and mechanistic insights into the channel and its ATPase motor SecA are important steps towards the elucidation of the allosteric crosstalk that mediates secretion. In this Review, we discuss recent biochemical, structural and mechanistic insights into the consecutive steps of the Sec pathway - sorting and targeting, translocation and release - in both co-translational and post-translational modes of export. The architecture and conformational dynamics of the SecYEG channel and its regulation by ribosomes, SecA and pre-proteins are highlighted. Moreover, we present conceptual models of the mechanisms and energetics of the Sec-pathway dependent secretion process in bacteria.
authors.affiliation: Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven (KU Leuven), B-3000 Leuven, Belgium.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Tsirigotaki
authors.affiliation: Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven (KU Leuven), B-3000 Leuven, Belgium.
authors.forename: Jozefien
authors.initials: J
authors.lastname: De Geyter
authors.affiliation: Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven (KU Leuven), B-3000 Leuven, Belgium.
authors.forename: Nikolina
authors.initials: N
authors.lastname: Šoštaric
authors.affiliation: Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven (KU Leuven), B-3000 Leuven, Belgium.
authors.forename: Anastassios
authors.initials: A
authors.lastname: Economou
authors.affiliation: Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, Katholieke Universiteit Leuven (KU Leuven), B-3000 Leuven, Belgium.
authors.forename: Spyridoula
authors.initials: S
authors.lastname: Karamanou
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D011487:Protein Conformation; D021382:Protein Sorting Signals / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology*; D000069816:SEC Translocation Channels / Q000378:metabolism*; D000081416:SecA Proteins; D015398:Signal Transduction / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D021382:Protein Sorting Signals; D000069816:SEC Translocation Channels; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins