title: Two-step and one-step secretion mechanisms in Gram-negative bacteria: contrasting the type IV secretion system and the chaperone-usher pathway of pilus biogenesis.
abstract: Gram-negative bacteria have evolved diverse secretion systems/machineries to translocate substrates across the cell envelope. These various machineries fulfil a wide variety of functions but are also essential for pathogenic bacteria to infect human or plant cells. Secretion systems, of which there are seven, utilize one of two secretion mechanisms: (i) the one-step mechanism, whereby substrates are translocated directly from the bacterial cytoplasm to the extracellular medium or into the eukaryotic target cell; (ii) the two-step mechanism, whereby substrates are first translocated across the bacterial inner membrane; once in the periplasm, substrates are targeted to one of the secretion systems that mediate transport across the outer membrane and released outside the bacterial cell. The present review provides an example for each of these two classes of secretion systems and contrasts the various solutions evolved to secrete substrates.
authors.affiliation: Institute of Structural and Molecular Biology, Birkbeck and University College London, Malet Street, London, WC1E 7HX, UK.
authors.forename: Ana Toste
authors.initials: AT
authors.lastname: Rêgo
authors.forename: Vidya
authors.initials: V
authors.lastname: Chandran
authors.forename: Gabriel
authors.initials: G
authors.lastname: Waksman
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D018407:Bacterial Physiological Phenomena; D003593:Cytoplasm / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006090:Gram-Negative Bacteria / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D018832:Molecular Chaperones; D011489:Protein Denaturation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; D018832:Molecular Chaperones; D037521:Virulence Factors; D000255:Adenosine Triphosphate