title: A prl mutation in SecY suppresses secretion and virulence defects of Listeria monocytogenes secA2 mutants.
abstract: The bulk of bacterial protein secretion occurs through the conserved SecY translocation channel that is powered by SecA-dependent ATP hydrolysis. Many Gram-positive bacteria, including the human pathogen Listeria monocytogenes, possess an additional nonessential specialized ATPase, SecA2. SecA2-dependent secretion is required for normal cell morphology and virulence in L. monocytogenes; however, the mechanism of export via this pathway is poorly understood. L. monocytogenes secA2 mutants form rough colonies, have septation defects, are impaired for swarming motility, and form small plaques in tissue culture cells. In this study, 70 spontaneous mutants were isolated that restored swarming motility to L. monocytogenes secA2 mutants. Most of the mutants had smooth colony morphology and septated normally, but all were lysozyme sensitive. Five representative mutants were subjected to whole-genome sequencing. Four of the five had mutations in proteins encoded by the lmo2769 operon that conferred lysozyme sensitivity and increased swarming but did not rescue virulence defects. A point mutation in secY was identified that conferred smooth colony morphology to secA2 mutants, restored wild-type plaque formation, and increased virulence in mice. This secY mutation resembled a prl suppressor known to expand the repertoire of proteins secreted through the SecY translocation complex. Accordingly, the ΔsecA2prlA1 mutant showed wild-type secretion levels of P60, an established SecA2-dependent secreted autolysin. Although the prl mutation largely suppressed almost all of the measurable SecA2-dependent traits, the ΔsecA2prlA1 mutant was still less virulent in vivo than the wild-type strain, suggesting that SecA2 function was still required for pathogenesis.
authors.affiliation: Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, USA.
authors.forename: Juliana
authors.initials: J
authors.lastname: Durack
authors.affiliation: Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Burke
authors.affiliation: Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, California, USA School of Public Health, University of California Berkeley, Berkeley, California, USA portnoy@berkeley.edu.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Portnoy
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008089:Listeria monocytogenes / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D008088:Listeriosis / Q000382:microbiology*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D021381:Protein Transport; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D013489:Suppression, Genetic; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins