High Salt Concentrations Increase Permeability through OmpC Channels of Escherichia coli

Kojima, Seiji; Nikaido, Hiroshi

doi:10.1074/jbc.m114.585869

Cited by 54 publications

(85 citation statements)

References 38 publications

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“…The authors suggested that, in contrast to the obvious exclusion due to reduced channel size, effects such as changes in the electric field at the constriction zone might have an impact on the channel permeability (17). Recent computational and experimental studies also suggested that the electrostatic profile inside the channel might play a major role in transit of polar molecules (18,19). Subsequently, the internal electrostatics of the mutant porins (OmpC20 and OmpC33) were analyzed in the absence of any antibiotic or metabolite, using water as a probe to sense the internal electric field (20).…”

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confidence: 99%

Molecular Basis of Filtering Carbapenems by Porins from β-Lactam-resistant Clinical Strains of Escherichia coli

Bajaj

Scorciapino

Moynié

et al. 2016

Journal of Biological Chemistry

100

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Integral membrane proteins known as porins are the major pathway by which hydrophilic antibiotics cross the outer membrane of Gram-negative bacteria. Single point mutations in porins can decrease the permeability of an antibiotic, either by reduction of channel size or modification of electrostatics in the channel, and thereby confer clinical resistance. Here, we investigate four mutant OmpC proteins from four different clinical isolates of Escherichia coli obtained sequentially from a single patient during a course of antimicrobial chemotherapy. OmpC porin from the first isolate (OmpC20) undergoes three consecutive and additive substitutions giving rise to OmpC26, OmpC28, and finally OmpC33. The permeability of two zwitterionic carbapenems, imipenem and meropenem, measured using liposome permeation assays and single channel electrophysiology differs significantly between OmpC20 and OmpC33. Molecular dynamic simulations show that the antibiotics must pass through the constriction zone of porins with a specific orientation, where the antibiotic dipole is aligned along the electric field inside the porin. We identify that changes in the vector of the electric field in the mutated porin, OmpC33, create an additional barrier by "trapping" the antibiotic in an unfavorable orientation in the constriction zone that suffers steric hindrance for the reorientation needed for its onward translocation. Identification and understanding the underlying molecular details of such a barrier to translocation will aid in the design of new antibiotics with improved permeation properties in Gram-negative bacteria.

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confidence: 99%

Molecular Basis of Filtering Carbapenems by Porins from β-Lactam-resistant Clinical Strains of Escherichia coli

Bajaj

Scorciapino

Moynié

et al. 2016

Journal of Biological Chemistry

100

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“…This construct was then inserted into pHSG575. The construction of pHSG575-based expression plasmids for E. coli ompF and ompC genes has been described earlier (13).…”

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confidence: 99%

Klebsiella pneumoniae Major Porins OmpK35 and OmpK36 Allow More Efficient Diffusion of β-Lactams than Their Escherichia coli Homologs OmpF and OmpC

2016

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Klebsiella pneumoniae, one of the most important nosocomial pathogens, is becoming a major problem in health care because of its resistance to multiple antibiotics, including cephalosporins of the latest generation and, more recently, even carbapenems. This is largely due to the spread of plasmid-encoded extended-spectrum ␤-lactamases. However, antimicrobial agents must first penetrate the outer membrane barrier in order to reach their targets, and hydrophilic and charged ␤-lactams presumably diffuse through the porin channels. Unfortunately, the properties of K. pneumoniae porin channels are largely unknown. In this study, we made clean deletions of K. pneumoniae porin genes ompK35 and ompK36 and examined the antibiotic susceptibilities and diffusion rates of ␤-lactams. The results showed that OmpK35 and OmpK36 produced larger more permeable channels than their Escherichia coli homologs OmpF and OmpC; OmpK35 especially produced a diffusion channel of remarkably high permeability toward lipophilic (benzylpenicillin) and large (cefepime) compounds. These results were also confirmed by expressing various porins in an E. coli strain lacking major porins and the major multidrug efflux pump AcrAB. Our data explain why the development of drug resistance in K. pneumoniae is so often accompanied by the mutational loss of its porins, especially OmpK35, in addition to the various plasmid-carried genes of antibiotic resistance, because even hydrolysis by ␤-lactamases becomes inefficient in producing high levels of resistance if the bacterium continues to allow a rapid influx of ␤-lactams through its wide porin channels. IMPORTANCEIn Gram-negative bacteria, drugs must first enter the outer membrane, usually through porin channels. Thus, the quantitative examination of influx rates is essential for the assessment of resistance mechanisms, yet no such studies exist for a very important nosocomial pathogen, Klebsiella pneumoniae. We found that the larger channel porin of this organism, OmpK35, produces a significantly larger channel than its Escherichia coli homolog, OmpF. This makes unmodified K. pneumoniae strains more susceptible to relatively large antibiotics, such as the third-and fourth-generation cephalosporins. Also, even the acquisition of powerful ␤-lactamases is not likely to make them fully resistant in the presence of such an effective influx process, explaining why so many clinical isolates of this organism lack porins. K lebsiella pneumoniae is currently one of the most important Gram-negative nosocomial pathogens, which are often carbapenem resistant (1), and its wide dissemination is helped by its capacity to survive in the hospital environment (2), presumably aided by the production of thick capsules. A remarkable feature of multidrug-resistant isolates of this species is the absence of porin(s) (for an early report, see reference 3, and for reviews, see references 4 and 5). K. pneumoniae produces two classical trimeric porins, OmpK35 and OmpK36, which are homologs of OmpF and OmpC of Escherichia col...

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“…This can also account for the low permeability of OmpC for anionic b-lactams [102,103]. Moreover, the replacement of all ten titratable residues that differ between OmpC and OmpF in the pore-lining region leads to the exchange of antibiotic permeation properties [104]. Together, these structural and functional data clearly demonstrate that the charge distribution at pore linings, but not pore size, is a critical parameter that physiologically distinguishes OmpC from OmpF.…”

Section: Porin Alterations In Clinical Isolatesmentioning

confidence: 98%

Stress responses, outer membrane permeability control and antimicrobial resistance in Enterobacteriaceae

2018

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Bacteria have evolved several strategies to survive a myriad of harmful conditions in the environment and in hosts. In Gramnegative bacteria, responses to nutrient limitation, oxidative or nitrosative stress, envelope stress, exposure to antimicrobials and other growth-limiting stresses have been linked to the development of antimicrobial resistance. This results from the activation of protective changes to cell physiology (decreased outer membrane permeability), resistance transporters (drug efflux pumps), resistant lifestyles (biofilms, persistence) and/or resistance mutations (target mutations, production of antibiotic modification/degradation enzymes). In targeting and interfering with essential physiological mechanisms, antimicrobials themselves are considered as stresses to which protective responses have also evolved. In this review, we focus on envelope stress responses that affect the expression of outer membrane porins and their impact on antimicrobial resistance. We also discuss evidences that indicate the role of antimicrobials as signaling molecules in activating envelope stress responses.

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High Salt Concentrations Increase Permeability through OmpC Channels of Escherichia coli

Cited by 54 publications

References 38 publications

Molecular Basis of Filtering Carbapenems by Porins from β-Lactam-resistant Clinical Strains of Escherichia coli

Molecular Basis of Filtering Carbapenems by Porins from β-Lactam-resistant Clinical Strains of Escherichia coli

Klebsiella pneumoniae Major Porins OmpK35 and OmpK36 Allow More Efficient Diffusion of β-Lactams than Their Escherichia coli Homologs OmpF and OmpC

Stress responses, outer membrane permeability control and antimicrobial resistance in Enterobacteriaceae

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