Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Comparative Study
. 1999 Oct;181(19):6142-51.
doi: 10.1128/JB.181.19.6142-6151.1999.

A Streptomyces coelicolor antibiotic regulatory gene, absB, encodes an RNase III homolog

B Price  1 , T Adamidis, R Kong, W Champness
Affiliations
Comparative Study

A Streptomyces coelicolor antibiotic regulatory gene, absB, encodes an RNase III homolog

B Price et al. J Bacteriol. 1999 Oct.

Abstract

Streptomyces coelicolor produces four genetically and structurally distinct antibiotics in a growth-phase-dependent manner. S. coelicolor mutants globally deficient in antibiotic production (Abs(-) phenotype) have previously been isolated, and some of these were found to define the absB locus. In this study, we isolated absB-complementing DNA and show that it encodes the S. coelicolor homolog of RNase III (rnc). Several lines of evidence indicate that the absB mutant global defect in antibiotic synthesis is due to a deficiency in RNase III. In marker exchange experiments, the S. coelicolor rnc gene rescued absB mutants, restoring antibiotic production. Sequencing the DNA of absB mutants confirmed that the absB mutations lay in the rnc open reading frame. Constructed disruptions of rnc in both S. coelicolor 1501 and Streptomyces lividans 1326 caused an Abs(-) phenotype. An absB mutation caused accumulation of 30S rRNA precursors, as had previously been reported for E. coli rnc mutants. The absB gene is widely conserved in streptomycetes. We speculate on why an RNase III deficiency could globally affect the synthesis of antibiotics.

PubMed Disclaimer

Figures

FIG. 1
FIG. 1
Defining absB-complementing sequences. Fragments from pTA108 used in cloning schemes outlined in the text are diagrammed. Those fragments capable of restoring the Abs+ phenotype to the absB mutants are shaded. Plasmid clones used in marker rescue experiments (pIJ963 derivatives) are designated pBK3xx, while clones derived from pIJ922 and pIJ702 are named pBK60x and pBK65x, respectively. The absB mutant alleles cloned into pIJ922 and pIJ702 that were unable to complement the absB mutants are designated by a hatched box. ORFs determined by sequence analysis are indicated by arrows. Relevant restriction sites are noted.
FIG. 2
FIG. 2
Sequence of the absB locus. Nucleotide and protein sequences of the absB gene and the 5′ end of the fpg gene are shown. PCR primer annealing sites are highlighted in boldface text. Putative ribosomal binding sites (rbs) and possible GTG start sites for AbsB and Fpg are underlined. The point mutations identified in absB mutants C120 and C175 are noted, as are the resulting amino acid changes. The frameshift in mutant C252 is also indicated. The highly conserved 10-amino-acid region common to all RNase III homologs is underlined. The double-stranded RNA binding domain, as defined in E. coli, is underlined. Stem-loop structures predicted by RNAFOLD are also indicated (>> <<).
FIG. 3
FIG. 3
Amino acid alignment of AbsB and RNase III homologs. Homologs are listed in the order of highest identity to AbsB (M. tuberculosis, 62.2%; B. subtilis, 40.9%; E. coli, 40.9%; C. burnetii, 39.7%; H. influenzae, 38.6%; M. genitalium, 35.0%; and S. pombe, 27.3%). Amino acid numbering is based on AbsB sequence (first 100 amino acids of S. pombe pac1 not shown) and was compiled by using PILEUP (University of Wisconsin GCG Group Package, version 9). The consensus is noted for amino acids conserved in ≥5 homologs. The dsRBD as defined for E. coli (α1-β1-β2-β3-α2 [31]) is noted; α-helices and β-sheets are highlighted with arrows. ∗, locations of amino acids altered in E. coli alleles rnc105 (G in a highly conserved 10-amino-acid box) and rnc70 (a highly conserved E).
FIG. 4
FIG. 4
(A) Genetic organization of the S. coelicolor absB locus. Coordinates of the ORFs shown are those of the Sanger Center S. coelicolor Sequencing Project (49). The sequencing project ORF names are also shown. absB corresponds to ORF SC7A1.16. ter indicates the stem-loop, likely to be a terminator, shown in Fig. 2. tsp indicates a potential location for a transcription start site. (B) Disruption of the S. coelicolor absB gene by integration of pBK314 (see Materials and Methods). The zigzag indicates truncation of the absB coding region.
FIG. 5
FIG. 5
rRNA processing in the absB mutant. Normalized concentrations of RNA from wild-type strain J1501, absB mutant C120, and C120 rescued to the wild-type phenotype with pBK310 (C120-310) were isolated from four time points (shown as hours of culture incubation) and run on a 1.5% agarose gel at low voltage for 16 h and then stained with ethidium bromide. Sporulation occurred by 54 h in all strains. Antibiotic production was also evident by 54 h in J1501 and C120-310.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Aceti D J, Champness W C. Transcriptional regulation of Streptomyces coelicolor pathway-specific antibiotic regulation by the absA and absB loci. J Bacteriol. 1998;180:3100–3106. - PMC - PubMed
    1. Adamidis A. Ph.D. dissertation. East Lansing: Michigan State University; 1994.
    1. Adamidis T, Champness W. Genetic analysis of absB, a Streptomyces coelicolor locus involved in global antibiotic regulation. J Bacteriol. 1992;174:4622–4628. - PMC - PubMed
    1. Adamidis T, Riggle P, Champness W. Mutations in a new Streptomyces coelicolor locus which globally block antibiotic biosynthesis but not sporulation. J Bacteriol. 1990;172:2962–2969. - PMC - PubMed
    1. Apirion D, Watson N. Mapping and characterization of a mutation in Escherichia coli that reduces the level of ribonuclease III specific for double-stranded ribonucleic acid. J Bacteriol. 1975;124:317–324. - PMC - PubMed

Publication types