title: Role of the periplasmic chaperones Skp, SurA, and DegQ in outer membrane protein biogenesis in Neisseria meningitidis.
abstract: The periplasmic chaperones Skp, SurA, and DegP are implicated in the biogenesis of outer membrane proteins (OMPs) in Escherichia coli. Here, we investigated whether these chaperones exert similar functions in Neisseria meningitidis. Although N. meningitidis does not contain a homolog of the protease/chaperone DegP, it does possess a homolog of another E. coli protein, DegQ, which can functionally replace DegP when overproduced. Hence, we examined whether in N. meningitidis, DegQ acts as a functional homolog of DegP. Single skp, surA, and degQ mutants were easily obtained, showing that none of these chaperones is essential in N. meningitidis. Furthermore, all combinations of double mutants were generated and no synthetic lethality was observed. The absence of SurA or DegQ did not affect OMP biogenesis. In contrast, the absence of Skp resulted in severely lower levels of the porins PorA and PorB but not of other OMPs. These decreased levels were not due to proteolytic activity of DegQ, since porin levels remained low in a skp degQ double mutant, indicating that neisserial DegQ is not a functional homolog of E. coli DegP. The absence of Skp resulted in lower expression of the porB gene, as shown by using a P(porB)-lacZ fusion. We found no cross-species complementation when Skp of E. coli or N. meningitidis was heterologously expressed in skp mutants, indicating that Skp functions in a species-specific manner. Our results demonstrate an important role for Skp but not for SurA or DegQ in OMP biogenesis in N. meningitidis.
authors.affiliation: Department of Molecular Microbiology, Utrecht University, Padualaan 8, 3584 CH Utrecht, Netherlands.
authors.forename: Elena B
authors.initials: EB
authors.lastname: Volokhina
authors.forename: Jan
authors.initials: J
authors.lastname: Grijpstra
authors.forename: Michiel
authors.initials: M
authors.lastname: Stork
authors.forename: Ingrid
authors.initials: I
authors.lastname: Schilders
authors.forename: Jan
authors.initials: J
authors.lastname: Tommassen
authors.forename: Martine P
authors.initials: MP
authors.lastname: Bos
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009345:Neisseria meningitidis / Q000235:genetics / Q000378:metabolism*; D018272:Porins
chemical_list: D001425:Bacterial Outer Membrane Proteins; D018832:Molecular Chaperones; D018272:Porins