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Characterization of the enzymes encoded by the anthrose biosynthetic operon of Bacillus anthracis.

ABSTRACT: Bacillus anthracis spores, the etiological agents of anthrax, possess a loosely fitting outer layer called the exosporium that is composed of a basal layer and an external hairlike nap. The filaments of the nap are formed by trimers of the collagenlike glycoprotein BclA. Multiple pentasaccharide and trisaccharide side chains are O linked to BclA. The nonreducing terminal residue of the pentasaccharide side chain is the unusual sugar anthrose. A plausible biosynthetic pathway for anthrose biosynthesis has been proposed, and an antABCD operon encoding four putative anthrose biosynthetic enzymes has been identified. In this study, we genetically and biochemically characterized the activities of these enzymes. We also used mutant B. anthracis strains to determine the effects on BclA glycosylation of individually inactivating the genes of the anthrose operon. The inactivation of antA resulted in the appearance of BclA pentasaccharides containing anthrose analogs possessing shorter side chains linked to the amino group of the sugar. The inactivation of antB resulted in BclA being replaced with only trisaccharides, suggesting that the enzyme encoded by the gene is a dTDP-?-L-rhamnose ?-1,3-L-rhamnosyl transferase that attaches the fourth residue of the pentasaccharide side chain. The inactivation of antC and antD resulted in the disappearance of BclA pentasaccharides and the appearance of a tetrasaccharide lacking anthrose. These phenotypes are entirely consistent with the proposed roles for the antABCD-encoded enzymes in anthrose biosynthesis. Purified AntA was then shown to exhibit ?-methylcrotonyl-coenzyme A (CoA) hydratase activity, as we predicted. Similarly, we confirmed that purified AntC had aminotransferase activity and that purified AntD displayed N-acyltransferase activity.

SUBMITTER: Dong S

PROVIDER: S-EPMC2944512 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature

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Characterization of the enzymes encoded by the anthrose biosynthetic operon of Bacillus anthracis.

Dong Shengli S McPherson Sylvia A SA Wang Yun Y Li Mei M Wang Pengfei P Turnbough Charles L CL Pritchard David G DG

Journal of bacteriology 20100730 19

Bacillus anthracis spores, the etiological agents of anthrax, possess a loosely fitting outer layer called the exosporium that is composed of a basal layer and an external hairlike nap. The filaments of the nap are formed by trimers of the collagenlike glycoprotein BclA. Multiple pentasaccharide and trisaccharide side chains are O linked to BclA. The nonreducing terminal residue of the pentasaccharide side chain is the unusual sugar anthrose. A plausible biosynthetic pathway for anthrose biosynt ...[more]

PMID: 20675481

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Project description:Purpose: Small regulatory RNAs (sRNAs) are short transcripts that base-pair to mRNA targets or interact with regulatory proteins. sRNA function has been extensively studied in Gram-negative bacteria; comparatively less is known about sRNAs in Firmicutes. Here we investigate two sRNAs encoded by the virulence plasmid pXO1 of Bacillus anthracis, the causative agent of anthrax. We designated the sRNAs as as “XrrA” and “XrrB” (for pXO1-encoded regulatory RNA). We constructed deletion mutants ∆xrrA, ∆xrrB, and ∆xrrA∆xrrB in an Ames strain background and compared gene expression of these mutants to that of the Ames-derived parent strain using RNA-seq. Methods: Total RNA from Ames strains UTA37 (Parent), UTA38 (∆xrrB), UTA39 (∆xrrA), UTA41 (∆xrrA∆xrrB) was isolated from cultures grown in CA-CO2 in triplicate, using saturated phenol: chloroform extraction. One microgram of pure and quality-checked RNA from each sample was subjected to Illumina sequencing by synthesis using a NextSeq550 sequencer. Sequencing by synthesis was performed to generate 75bp paired-end reads. Two 130M-read sequencing runs (Run1 and Run2) were performed and an average of 31M reads per sample were obtained. Results: All bioinformatic analysis was performed using the publicly available Galaxy web resource (https://usegalaxy.org/). Comparison of the transcriptomes of a virulent Ames-derived strain to isogenic sRNA-null mutants revealed multiple 4.0- to >100-fold differences in gene expression. Deletion of xrrA resulted in 50 transcripts showing a ≥ 4.0-fold change in expression compared to the parent strain. In contrast, deletion of xrrB led to one transcript having a ≥ 4.0-fold change in expression compared to the parent strain. In the ∆xrrA∆xrrB mutant, levels of 116 transcripts were affected with a fold-change of ≥ 4.0. Many sRNA-regulated targets were chromosome genes associated with branched-chain amino acid metabolism, proteolysis, and transmembrane transport. Conclusions: In this work, we provide experimental evidence for sRNA-mediated regulation in the mammalian pathogen B. anthracis. XrrA and XrrB are the first regulatory RNAs examined in B. anthracis and are shown here to have multiple effects on gene expression in this pathogen. The data suggest distinct regulatory roles for XrrA, as well as some functional overlap between XrrA and XrrB.

Dataset Information

Characterization of the enzymes encoded by the anthrose biosynthetic operon of Bacillus anthracis.

Publications

Characterization of the enzymes encoded by the anthrose biosynthetic operon of Bacillus anthracis.

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