Factors Affecting the Folding of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> OprF Porin into the One-Domain Open Conformer

ABSTRACT Pseudomonas aeruginosa OprF is a largely monomeric outer membrane protein that allows the slow, nonspecific transmembrane diffusion of solutes. This protein folds into two different conformers, with the majority conformer folding into a two-domain conformation that has no porin activity and...

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Autores principales:	Etsuko Sugawara, Keiji Nagano, Hiroshi Nikaido
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2010
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/1724621816e448869063136c62ceed80
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spelling	oai:doaj.org-article:1724621816e448869063136c62ceed802021-11-15T15:38:15ZFactors Affecting the Folding of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> OprF Porin into the One-Domain Open Conformer10.1128/mBio.00228-102150-7511https://doaj.org/article/1724621816e448869063136c62ceed802010-10-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00228-10https://doaj.org/toc/2150-7511ABSTRACT Pseudomonas aeruginosa OprF is a largely monomeric outer membrane protein that allows the slow, nonspecific transmembrane diffusion of solutes. This protein folds into two different conformers, with the majority conformer folding into a two-domain conformation that has no porin activity and the minority conformer into a one-domain conformation with high porin activity and presumably consisting of a large β barrel. We examined the factors that control the divergent folding pathways of OprF. OprF contains four Cys residues in the linker region connecting the N-terminal β-barrel domain and the C-terminal globular domain in the majority conformer. Prevention of disulfide bond formation either by expression of OprF in an Escherichia coli dsbA strain grown with dithiothreitol or by replacement of all Cys residues with serine (CS OprF) increased the specific pore-forming activity of OprF significantly. Replacement of Phe160 with Ile at the end of the β-barrel termination signal as well as replacement of Lys164 in the linker region with Gly, Cys, or Glu increased porin activity 2-fold. Improving a potential β-barrel termination signal in the periplasmic domain by replacement of Asp211 with asparagine also increased porin activity. The porin activity could be improved about 5-fold by the combination of these replacements. OprF mutants with higher porin activity were shown to contain more one-domain conformers by surface labeling of the A312C residue in intact cells, as this residue is located in the periplasmic domain in the two-domain conformers. Finally, when the OprF protein was expressed in an E. coli strain lacking the periplasmic chaperone Skp, the CS OprF protein exhibited increased pore-forming activity. IMPORTANCE High intrinsic levels of resistance to many antimicrobial agents, seen in Gram-negative bacterial species such as Pseudomonas aeruginosa and Acinetobacter species, are largely due to the extremely low permeability of their major porin OprF and OmpA. Because this low permeability is caused by the fact that these proteins mostly fold into a two-domain conformer without pores, knowledge as to what conditions increase the production of the pore-forming minority conformer may lead to dramatic improvements in the treatment of infections by these bacteria. We have found several factors that increase the proportion of the pore-forming conformer up to 5-fold. Although these studies were done with Escherichia coli, they may serve as the starting point for the design of strategies for improvement of antimicrobial therapy for these difficult-to-treat pathogens, some strains of which have now attained the “pan-resistant” status.Etsuko SugawaraKeiji NaganoHiroshi NikaidoAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 1, Iss 4 (2010)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Etsuko Sugawara Keiji Nagano Hiroshi Nikaido Factors Affecting the Folding of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> OprF Porin into the One-Domain Open Conformer
description	ABSTRACT Pseudomonas aeruginosa OprF is a largely monomeric outer membrane protein that allows the slow, nonspecific transmembrane diffusion of solutes. This protein folds into two different conformers, with the majority conformer folding into a two-domain conformation that has no porin activity and the minority conformer into a one-domain conformation with high porin activity and presumably consisting of a large β barrel. We examined the factors that control the divergent folding pathways of OprF. OprF contains four Cys residues in the linker region connecting the N-terminal β-barrel domain and the C-terminal globular domain in the majority conformer. Prevention of disulfide bond formation either by expression of OprF in an Escherichia coli dsbA strain grown with dithiothreitol or by replacement of all Cys residues with serine (CS OprF) increased the specific pore-forming activity of OprF significantly. Replacement of Phe160 with Ile at the end of the β-barrel termination signal as well as replacement of Lys164 in the linker region with Gly, Cys, or Glu increased porin activity 2-fold. Improving a potential β-barrel termination signal in the periplasmic domain by replacement of Asp211 with asparagine also increased porin activity. The porin activity could be improved about 5-fold by the combination of these replacements. OprF mutants with higher porin activity were shown to contain more one-domain conformers by surface labeling of the A312C residue in intact cells, as this residue is located in the periplasmic domain in the two-domain conformers. Finally, when the OprF protein was expressed in an E. coli strain lacking the periplasmic chaperone Skp, the CS OprF protein exhibited increased pore-forming activity. IMPORTANCE High intrinsic levels of resistance to many antimicrobial agents, seen in Gram-negative bacterial species such as Pseudomonas aeruginosa and Acinetobacter species, are largely due to the extremely low permeability of their major porin OprF and OmpA. Because this low permeability is caused by the fact that these proteins mostly fold into a two-domain conformer without pores, knowledge as to what conditions increase the production of the pore-forming minority conformer may lead to dramatic improvements in the treatment of infections by these bacteria. We have found several factors that increase the proportion of the pore-forming conformer up to 5-fold. Although these studies were done with Escherichia coli, they may serve as the starting point for the design of strategies for improvement of antimicrobial therapy for these difficult-to-treat pathogens, some strains of which have now attained the “pan-resistant” status.
format	article
author	Etsuko Sugawara Keiji Nagano Hiroshi Nikaido
author_facet	Etsuko Sugawara Keiji Nagano Hiroshi Nikaido
author_sort	Etsuko Sugawara
title	Factors Affecting the Folding of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> OprF Porin into the One-Domain Open Conformer
title_short	Factors Affecting the Folding of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> OprF Porin into the One-Domain Open Conformer
title_full	Factors Affecting the Folding of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> OprF Porin into the One-Domain Open Conformer
title_fullStr	Factors Affecting the Folding of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> OprF Porin into the One-Domain Open Conformer
title_full_unstemmed	Factors Affecting the Folding of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> OprF Porin into the One-Domain Open Conformer
title_sort	factors affecting the folding of <named-content content-type="genus-species">pseudomonas aeruginosa</named-content> oprf porin into the one-domain open conformer
publisher	American Society for Microbiology
publishDate	2010
url	https://doaj.org/article/1724621816e448869063136c62ceed80
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Factors Affecting the Folding of <named-content content-type="genus-species">Pseudomonas aeruginosa</named-content> OprF Porin into the One-Domain Open Conformer

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