Posttranslational modifications in microcin B17 define an additional class of DNA gyrase inhibitor.

Yorgey, Peter; Lee, Jonathan; Kordel, Johann; Vivas, Eugenio I.; Warner, Philip; Jebaratnam, David J.; Kolter, Roberto

doi:10.1073/pnas.91.10.4519

Cited by 157 publications

(153 citation statements)

References 25 publications

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“…The E. coli SbmA protein is thought to be involved in the uptake of microcin B17 on the basis of the observations that sbmA mutants exhibit a complete resistance to microcin B17 that is added to medium exogeneously but that the mutants remain sensitive to microcin B17 that is produced intracellularly (29). Recently, SbmA was also implicated in the uptake of microcin J25 and bleomycin, since sbmA mutants show a complete resistance to microcin J25 and an increased resistance to bleomycin (41,51). We examined whether the R. meliloti bacA gene could suppress the resistance of E. coli sbmA mutants to these compounds.…”

Section: Resultsmentioning

confidence: 99%

“…Homologs of the bacA gene are found in a variety of bacteria (21). The Escherichia coli homolog of BacA, SbmA, has been implicated in the uptake of microcin B17, microcin J25 (formerly microcin 25 [43]), and bleomycin (29,41,51). In view of the degree of structural similarity between the BacA and SbmA proteins (64% identity), it has been hypothesized that BacA may be required for the uptake of some compound that plays an important role in bacteroid development (21), although there has been no direct evidence for functional similarity between the two proteins.…”

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confidence: 99%

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Genetic analysis of the Rhizobium meliloti bacA gene: functional interchangeability with the Escherichia coli sbmA gene and phenotypes of mutants

1997

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The Rhizobium meliloti bacA gene encodes a function that is essential for bacterial differentiation into bacteroids within plant cells in the symbiosis between R. meliloti and alfalfa. An Escherichia coli homolog of BacA, SbmA, is implicated in the uptake of microcin B17, microcin J25 (formerly microcin 25), and bleomycin. When expressed in E. coli with the lacZ promoter, the R. meliloti bacA gene was found to suppress all the known defects of E. coli sbmA mutants, namely, increased resistance to microcin B17, microcin J25, and bleomycin, demonstrating the functional similarity between the two proteins. The R. meliloti bacA386::TnphoA mutant, as well as a newly constructed bacA deletion mutant, was found to show increased resistance to bleomycin. However, it also showed increased resistance to certain aminoglycosides and increased sensitivity to ethanol and detergents, suggesting that the loss of bacA function causes some defect in membrane integrity. The E. coli sbmA gene suppressed all these bacA mutant phenotypes as well as the Fix ؊ phenotype when placed under control of the bacA promoter. Taken together, these results strongly suggest that the BacA and SbmA proteins are functionally similar and thus provide support for our previous hypothesis that BacA may be required for uptake of some compound that plays an important role in bacteroid development. However, the additional phenotypes of bacA mutants identified in this study suggest the alternative possibility that BacA may be needed for membrane integrity, which is likely to be critically important during the early stages of bacterial differentiation within plant cells.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Genetic analysis of the Rhizobium meliloti bacA gene: functional interchangeability with the Escherichia coli sbmA gene and phenotypes of mutants

1997

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“…These genes and the organization of the cluster are reminiscent of the lantibiotic and microcin biosynthetic machinery, which has been characterized in other bacteria (30)(31)(32). In particular, the microcin B17 peptide contains heterocycles (18,33), whereas microcin J25 (21, 34) is cyclic. However, the combination of functionality (heterocyclization and cyclization) is thus far unique to the pat cluster.…”

Section: Resultsmentioning

confidence: 99%

Patellamide A and C biosynthesis by a microcin-like pathway inProchloron didemni, the cyanobacterial symbiont ofLissoclinum patella

Schmidt

Nelson

Rasko

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

552

717

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Prochloron spp. are obligate cyanobacterial symbionts of many didemnid family ascidians. It has been proposed that the cyclic peptides of the patellamide class found in didemnid extracts are synthesized by Prochloron spp., but studies in which host and symbiont cells are separated and chemically analyzed to identify the biosynthetic source have yielded inconclusive results. As part of the Prochloron didemni sequencing project, we identified patellamide biosynthetic genes and confirmed their function by heterologous expression of the whole pathway in Escherichia coli. The primary sequence of patellamides A and C is encoded on a single ORF that resembles a precursor peptide. We propose that this prepatellamide is heterocyclized to form thiazole and oxazoline rings, and the peptide is cleaved to yield the two cyclic patellamides, A and C. This work represents the full sequencing and functional expression of a marine natural-product pathway from an obligate symbiont. In addition, a related cluster was identified in Trichodesmium erythraeum IMS101, an important bloom-forming cyanobacterium.heterocycle ͉ tunicate ͉ ascidian ͉ genome sequencing ͉ lantibiotic

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“…The structure of MccB17, aside from the oxazoles and thiazoles, is essentially a glycine linker (3,4), suggesting that the heterocycles are the important structural determinants of the antibiotic activity. Oxazoles and thiazoles are found in a wide variety of natural products that target a diverse array of cellular molecules (20).…”

Section: Steady-state Analysis Of Cleavable Complex Induced By Mccb17mentioning

confidence: 99%

“…The production of mature MccB17 ( Fig. 1) involves posttranslational modification of a 69-residue polypeptide-precursor to generate two thiazoles, two oxazoles, and two 4,2-fused bisheterocycles (3,4), followed by cleavage of the 26-residue leader sequence by an unidentified protease (5,6). Exposure of sensitive bacteria to MccB17 results in inhibition of DNA synthesis, induction of the SOS response in cells with active replication, mutagenic effects, and DNA degradation (7).…”

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In vitro characterization of DNA gyrase inhibition by microcin B17 analogs with altered bisheterocyclic sites

Zamble

Miller

Heddle

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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M icrocins are a class of small antibiotics (Ͻ10 kDa) produced and excreted by some strains of Enterobacteriaceae at the stationary phase of growth (1). Microcin B17 (MccB17) is a ribosomally synthesized compound that is produced in Escherichia coli harboring the plasmid-borne mcb operon, which contains the genes necessary for antibiotic synthesis, dedicated export, and immunity (2). The production of mature MccB17 ( Fig. 1) involves posttranslational modification of a 69-residue polypeptide-precursor to generate two thiazoles, two oxazoles, and two 4,2-fused bisheterocycles (3, 4), followed by cleavage of the 26-residue leader sequence by an unidentified protease (5, 6). Exposure of sensitive bacteria to MccB17 results in inhibition of DNA synthesis, induction of the SOS response in cells with active replication, mutagenic effects, and DNA degradation (7). These observations suggest that MccB17 is either a DNAdamaging agent or targets a key DNA-processing pathway such as replication.Genetic experiments designed to identify the target of MccB17 resulted in the isolation and characterization of a mutation in the B subunit of DNA gyrase (8). Strains carrying this mutation, a Trp-Arg substitution at position 751, exhibited increased resistance to MccB17 and a decrease in MccB17-induced DNA cleavage. Gyrase is a prokaryotic type II topoisomerase that introduces negative supercoils into DNA (9, 10). During the reaction, the enzyme passes through a transient intermediate in which two tyrosine hydroxyl groups form phosphodiester bonds with the exposed 5Ј phosphates of doublestrand cleaved DNA. This intermediate allows the enzyme to pull the ends of the DNA break apart to form a gate through which another DNA segment is passed. The quinolone family of drugs traps this covalent intermediate, known as the cleavable complex, and the accumulation of this complex is monitored in vitro by treatment with SDS and proteinase K, which releases linear DNA (11-13). The ternary complex blocks passage of the replication fork (14, 15), which may initiate the bactericidal activity of the quinolones, although the exact irreversible lethal event has not been firmly established (16). Recent in vitro analysis of the interaction between gyrase and MccB17 revealed that this antibiotic also causes accumulation of the cleavable complex in a manner similar to that of the quinolone drugs (17).Gyrase is the target of several classes of clinically successful drugs, including the quinolones and the coumarins (11, 13); however, the emergence of resistant strains is an incentive to elucidate the mechanism of action of existing drugs and develop new candidates. The identification of gyrase as a target of MccB17 provides an opportunity to analyze the structurefunction relationship of this unusual antibiotic. The experiments described here investigate the effects of modifying MccB17 at the sites of the tandem heterocycles, labeled A and B (Fig. 1). The interaction of MccB17 analogs with DNA gyrase was evaluated by measuring the rate of formation of the ...

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Posttranslational modifications in microcin B17 define an additional class of DNA gyrase inhibitor.

Cited by 157 publications

References 25 publications

Genetic analysis of the Rhizobium meliloti bacA gene: functional interchangeability with the Escherichia coli sbmA gene and phenotypes of mutants

Genetic analysis of the Rhizobium meliloti bacA gene: functional interchangeability with the Escherichia coli sbmA gene and phenotypes of mutants

Patellamide A and C biosynthesis by a microcin-like pathway inProchloron didemni, the cyanobacterial symbiont ofLissoclinum patella

In vitro characterization of DNA gyrase inhibition by microcin B17 analogs with altered bisheterocyclic sites

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