title: PpiA, a surface PPIase of the cyclophilin family in Lactococcus lactis.
abstract: BACKGROUND
  Protein folding in the envelope is a crucial limiting step of protein export and secretion. In order to better understand this process in Lactococcus lactis, a lactic acid bacterium, genes encoding putative exported folding factors like Peptidyl Prolyl Isomerases (PPIases) were searched for in lactococcal genomes.
  
  
  RESULTS
  In L. lactis, a new putative membrane PPIase of the cyclophilin subfamily, PpiA, was identified and characterized. ppiA gene was found to be constitutively expressed under normal and stress (heat shock, H(2)O(2)) conditions. Under normal conditions, PpiA protein was synthesized and released from intact cells by an exogenously added protease, showing that it was exposed at the cell surface. No obvious phenotype could be associated to a ppiA mutant strain under several laboratory conditions including stress conditions, except a very low sensitivity to H(2)O(2). Induction of a ppiA copy provided in trans had no effect i) on the thermosensitivity of an mutant strain deficient for the lactococcal surface protease HtrA and ii) on the secretion and stability on four exported proteins (a highly degraded hybrid protein and three heterologous secreted proteins) in an otherwise wild-type strain background. However, a recombinant soluble form of PpiA that had been produced and secreted in L. lactis and purified from a culture supernatant displayed both PPIase and chaperone activities.
  
  
  CONCLUSIONS
  Although L. lactis PpiA, a protein produced and exposed at the cell surface under normal conditions, displayed a very moderate role in vivo, it was found, as a recombinant soluble form, to be endowed with folding activities in vitro.
authors.affiliation: INRA, UMR1319 Micalis (Microbiologie de l'Alimentation au service de la Santé), Domaine de Vilvert, Jouy-en-Josas, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Trémillon
authors.forename: Eric
authors.initials: E
authors.lastname: Morello
authors.forename: Daniel
authors.initials: D
authors.lastname: Llull
authors.forename: Rabia
authors.initials: R
authors.lastname: Mazmouz
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Gratadoux
authors.forename: Alain
authors.initials: A
authors.lastname: Guillot
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Chapot-Chartier
authors.forename: Laura
authors.initials: L
authors.lastname: Monlezun
authors.forename: Véronique
authors.initials: V
authors.lastname: Solé
authors.forename: Hervé
authors.initials: H
authors.lastname: Ginisty
authors.forename: Isabelle
authors.initials: I
authors.lastname: Poquet
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology* / Q000235:genetics; D021983:Cyclophilins / Q000235:genetics / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D013294:Lactococcus lactis / Q000201:enzymology* / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D019696:Peptidylprolyl Isomerase / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding; D013312:Stress, Physiological / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D016877:Oxidants; D006861:Hydrogen Peroxide; D021983:Cyclophilins; D019696:Peptidylprolyl Isomerase