Stable albicidin resistance in Escherichia coli involves an altered outer-membrane nucleoside uptake system

Birch, Robert G.; Pemberton, John; Basnayake, W. V. Shiromi

doi:10.1099/00221287-136-1-51

Cited by 38 publications

(53 citation statements)

References 18 publications

(13 reference statements)

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“…The exquisite sensitivity is due to illicit uptake of albicidins through a nucleoside uptake channel (Birch et al, 1990). Inhibition of DNA replication in bacteria and plastids is the primary mechanism of action (Birch & Patil, 1985b, 1987.…”

Section: Introductionmentioning

confidence: 99%

Identification of the essential histidine residue for high-affinity binding of AlbA protein to albicidin antibiotics

Weng

et al. 2003

Microbiology

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The albA gene from Klebsiella oxytoca encodes a protein that binds albicidin phytotoxins and antibiotics with high affinity. Previously, it has been shown that shifting pH from 6 to 4 reduces binding activity of AlbA by about 30 %, indicating that histidine residues might be involved in substrate binding. In this study, molecular analysis of the albA coding region revealed sequence discrepancies with the albA sequence reported previously, which were probably due to sequencing errors. The albA gene was subsequently cloned from K. oxytoca ATCC 13182 T to establish the revised sequence. Biochemical and molecular approaches were used to determine the functional role of four histidine residues (His 78 , His 125 , His 141 and His 189 ) in the corrected sequence for AlbA. Treatment of AlbA with diethyl pyrocarbonate (DEPC), a histidine-specific alkylating reagent, reduced binding activity by about 95 %. DEPC treatment increased absorbance at 240-244 nm by an amount indicating conversion to N-carbethoxyhistidine of a single histidine residue per AlbA molecule. Pretreatment with albicidin protected AlbA against modification by DEPC, with a 1: 1 molar ratio of albicidin to the protected histidine residues. Based on protein secondary structure and amino acid surface probability indices, it is predicted that His 125 might be the residue required for albicidin binding. Mutation of His 125 to either alanine or leucine resulted in about 32 % loss of binding activity, and deletion of His 125 totally abolished binding activity. Mutation of His 125 to arginine and tyrosine had no effect. These results indicate that His 125 plays a key role either in an electrostatic interaction between AlbA and albicidin or in the conformational dynamics of the albicidin-binding site.

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Section: Introductionmentioning

confidence: 99%

Identification of the essential histidine residue for high-affinity binding of AlbA protein to albicidin antibiotics

Weng

et al. 2003

Microbiology

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“…Interestingly, loop 3, which is normally very large in classical porins, is minute here and loops 6 and 7 are relatively large. The Tsx channel functions in the uptake of an antibiotic albicidin, and albicidin-resistant mutants contain alterations in this protein (61). Identification of mutational alterations showed that residues close to the loop-barrel junctions in loops 1, 6, and 7 are important in substrate recognition (211)…”

Section: Specific Channelsmentioning

confidence: 99%

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

Nikaido

2003

Microbiol Mol Biol Rev

3,784

3,800

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Gram-negative bacteria characteristically are surrounded by an additional membrane layer, the outer membrane. Although outer membrane components often play important roles in the interaction of symbiotic or pathogenic bacteria with their host organisms, the major role of this membrane must usually be to serve as a permeability barrier to prevent the entry of noxious compounds and at the same time to allow the influx of nutrient molecules. This review summarizes the development in the field since our previous review (H. Nikaido and M. Vaara, Microbiol. Rev. 49:1-32, 1985) was published. With the discovery of protein channels, structural knowledge enables us to understand in molecular detail how porins, specific channels, TonB-linked receptors, and other proteins function. We are now beginning to see how the export of large proteins occurs across the outer membrane. With our knowledge of the lipopolysaccharide-phospholipid asymmetric bilayer of the outer membrane, we are finally beginning to understand how this bilayer can retard the entry of lipophilic compounds, owing to our increasing knowledge about the chemistry of lipopolysaccharide from diverse organisms and the way in which lipopolysaccharide structure is modified by environmental conditions

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“…It also inhibits replication of bacteriophages T4 and T7 and plastid DNA replication, resulting in blocked chloroplast differentiation and the chlorotic streaks in sugarcane that are characteristic of the disease (4,(6)(7)(8)(9). Genes for resistance to albicidin have been cloned from Klebsiella oxytoca (37), Alcaligenes denitrificans (2), and Pantoea dispersa (syn.…”

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confidence: 99%

“…Genes for resistance to albicidin have been cloned from Klebsiella oxytoca (37), Alcaligenes denitrificans (2), and Pantoea dispersa (syn. Erwinia herbicola) (40, 41), and several resistance mechanisms have been identified (9,37,40,41).Although albicidin has been partially characterized as a lowmolecular-weight antibiotic that contains 38 carbon atoms with several aromatic rings (5), its chemical structure is unknown. The biosynthetic pathway to albicidin and the molecular genetic basis of albicidin production have not yet been studied.…”

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At least two separate gene clusters are involved in albicidin production by Xanthomonas albilineans

et al. 1996

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Transposon mutagenesis was used to obtain mutations affecting production of the toxin albicidin in Xanthomonas albilineans, which causes leaf scald disease of sugarcane and is also pathogenic to corn. Transposon Tn5-gusA inserted randomly into genomic DNA of X. albilineans Xa23R1 at a frequency of 10 ؊4 to 10 ؊5 per recipient after conjugal transfer from Escherichia coli. Fifty prototrophic mutants defective in albicidin production were isolated from 7,100 Tn5-gusA insertional derivatives tested for toxin production by an antibiosis bioassay. EcoRI fragments containing Tn5 flanking sequences from two mutants (AM15 and AM40) were cloned and used to probe a wild-type Xa23R1 DNA library by colony hybridization. Nine cosmids showed homology to the AM15 probe, and six showed homology to the AM40 probe. Four cosmid clones hybridized to both probes. Forty-five of the 50 defective mutants were restored to albicidin production with two overlapping cosmid clones. Restriction mapping showed that these mutants span a genomic region of about 48 kb. At least one other gene cluster is also involved in albicidin production in Xa23R1. DNA fragments from the 48-kb cluster proved to be very specific to X. albilineans. Some mutants affected in albicidin production retain their ability to colonize sugarcane cultivated in vitro.Xanthomonas albilineans is a systemic, xylem-invading pathogen that causes leaf scald disease of sugarcane (interspecific hybrids of Saccharum species) (28). Leaf scald symptoms include chlorosis, rapid wilting, and plant death. Symptoms frequently become apparent only after a long latent period. Chlorosis-inducing strains of the pathogen produce several toxic compounds which appear to play a role in pathogenesis. Spontaneous Tox Ϫ mutants of X. albilineans or mutants obtained after nitrosoguanidine, ethyl methane sulfonate, or UV mutagenesis were unable to cause systemic chlorosis in sugarcane (7). The major toxic component, named albicidin, is the only antibiotic known to be produced by Xanthomonas spp. However, toxin production by some pathovars of Xanthomonas campestris, such as X. campestris pv. vasculorum, another pathogen of sugarcane, has been reported (17, 18).Albicidin inhibits prokaryotic DNA replication and is bactericidal to a range of gram-positive and gram-negative bacteria (5). It also inhibits replication of bacteriophages T4 and T7 and plastid DNA replication, resulting in blocked chloroplast differentiation and the chlorotic streaks in sugarcane that are characteristic of the disease (4, 6-9). Genes for resistance to albicidin have been cloned from Klebsiella oxytoca (37), Alcaligenes denitrificans (2), and Pantoea dispersa (syn. Erwinia herbicola) (40, 41), and several resistance mechanisms have been identified (9,37,40,41).Although albicidin has been partially characterized as a lowmolecular-weight antibiotic that contains 38 carbon atoms with several aromatic rings (5), its chemical structure is unknown. The biosynthetic pathway to albicidin and the molecular genetic basis of albicidin pr...

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Stable albicidin resistance in Escherichia coli involves an altered outer-membrane nucleoside uptake system

Cited by 38 publications

References 18 publications

Identification of the essential histidine residue for high-affinity binding of AlbA protein to albicidin antibiotics

Identification of the essential histidine residue for high-affinity binding of AlbA protein to albicidin antibiotics

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

At least two separate gene clusters are involved in albicidin production by Xanthomonas albilineans

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