Summary auto-generated
This review analyzes the two-component signal transduction systems (TCSs) of Streptomyces coelicolor, a soil bacterium with a complex developmental life cycle. The S. coelicolor genome contains 84 sensor kinase (SK) genes and 80 response regulator (RR) genes, with 67 SK-RR pairs suggesting functional two-component systems. Additionally, there are 17 unpaired SKs and 13 orphan RRs. The paired SKs and RRs represent 0.86% of total genes, substantially higher than typical free-living bacteria, suggesting the organism is well-equipped to respond to diverse environmental signals. The authors classify SKs into five groups (I, II, IIIa, IIIb, and IV) based on conserved histidine domains and identify novel sensor domains, including GAF and PAS domains that likely bind small ligands and sense oxygen/light. Several characterized TCSs include PhoPR (phosphate sensing), CseBC (cell wall stress), VanRS (vancomycin resistance), KdpDE (osmotic stress), and AbsA (antibiotic production regulation). Most TCS functions remain unknown, though sequence analysis and available phenotypic data provide insights into their potential roles in development, metabolism, and stress response.
Key findings
- S. coelicolor contains 84 sensor kinases and 80 response regulators, with 67 forming functional pairs; 13 orphan RRs and 17 unpaired SKs also present
- SKs are classified into five groups with distinct characteristics; group II and IIIa SKs are most prevalent and pair with NarL and OmpR family RRs respectively
- Seven SKs contain GAF domains and six contain PAS domains, suggesting ligand-binding and redox/light-sensing capabilities
- Characterized TCSs regulate phosphate uptake, cell wall integrity, vancomycin resistance, osmotic stress, and antibiotic production
- The proportion of TCS genes (0.86% of total) is significantly higher than in other free-living bacteria, indicating enhanced environmental responsiveness
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Abstract
Streptomyces coelicolor is a Gram-positive soil bacterium that undergoes a complex developmental life cycle. The genome sequence of this organism was recently completed and has revealed the presence of over 60 sigma factors and a multitude of other transcriptional regulators, with a significant number of these being putative two-component signal transduction proteins. The authors have used the criteria established by Hoch and co-workers (Fabret et al., 1999, J Bacteriol 181, 19751983) to identify sensor kinase and response regulator genes encoded within the S. coelicolor genome. This analysis has revealed the presence of 84 sensor kinase genes, 67 of which lie adjacent to genes encoding response regulators. This strongly suggests that these paired genes encode two-component systems. In addition there are 13 orphan response regulators encoded in the genome, several of which have already been characterized and are implicated in development and antibiotic production, and 17 unpaired and as yet uncharacterized sensor kinases. This article attempts to infer useful information from sequence analysis and reviews what is currently known about the two-component systems, unpaired sensor kinases and orphan response regulators of S. coelicolor from both published reports and the authors' own unpublished data.