Genetic and transcriptional analysis of absA, an antibiotic gene cluster-linked two-component system that regulates multiple antibiotics in Streptomyces coelicolor

In Streptomyces coelicolor, the AbsA1-AbsA2 two-component system regulates the expression of multiple antibiotic gene clusters. Here, we show that the response regulator encoded by the absA2 gene is a negative regulator of these antibiotic gene clusters. A genetic analysis shows that the phosphorylated form of the AbsA2 response regulator (phospho-AbsA2), generated by the cognate AbsA1 sensor histidine kinase, is required for normal growth phase regulation of antibiotic synthesis. In the absence of phospho-AbsA2, antibiotics are produced earlier and more abundantly. Overexpression of AbsA1 also deregulates antibiotic synthesis, apparently shifting the AbsA1 protein from a kinase-active to a phospho-AbsA2 phosphatase-active form. The absA1 and absA2 genes, which are adjacent, are located in one of the antibiotic gene clusters that they regulate, the cluster for the calcium-dependent antibiotic (CDA). The absA genes themselves are growth phase regulated, with phospho-AbsA2 responsible for growth phase-related positive autoregulation. We discuss the possible role and mechanism of AbsA-mediated regulation of antibiotic synthesis in the S. coelicolor life cycle.     

Structure of ribulose 1,5-bisphosphate carboxylase/oxygenase gene cluster from a thermophilic hydrogen-oxidizing bacterium, Hydrogenophilus thermoluteolus, and phylogeny of the fructose 1,6-bisphosphate aldolase encoded by cbbA in the cluster

Four genes, cbbO, cbbY, cbbA, and the pyruvate kinase gene (pyk), were found downstream of ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) genes, cbbLS, from a thermophilic hydrogen-oxidizing bacterium, Hydrogenophilus thermoluteolus (formerly Pseudomonas hydrogenothermophila). cbbO was similar to norD in the denitrification gene cluster, and cbbY was similar to cbbY from other autotrophic bacteria. cbbA encoded fructose 1,6-bisphosphate aldolase (FBP aldolase); however, CbbA was little similar to other CbbA proteins. When CbbA was overexpressed in Escherichia coli, overproduction of CbbA was detected by SDS-PAGE. However, the cell extract had slightly higher activity than a cell extract of E. coli without cbbA. Phylogenetic analysis showed class II FBP aldolase divided into classes IIA and IIB, and that CbbA from H. thermoluteolus was in class IIA. Activities of RubisCO and FBP aldolase were examined under autotrophic, mixotrophic, and heterotrophic conditions. The activities of the two enzymes were regulated independently.     

Rcs双组分调节系统对细菌环境应答的分子调控研究进展

荚膜异多糖酸合成调节(Regulator of Capsule Synthesis,Rcs)系统是存在于许多肠杆菌科细菌中非典型的双组分调节系统,由3种核心蛋白(跨膜感应激酶RcsC、跨膜蛋白RcsD和响应调节剂RcsB)及多种辅助蛋白共同构成.Rcs系统能整合环境信号、调节基因表达并改变细菌的生理行为.近年来,对细菌...     

Nitric oxide regulated two-component signaling in Pseudoalteromonas atlantica

Bacteria employ two-component signaling to detect and respond to environmental stimuli. In essence, two-component signaling relies on a protein called a response regulator that can elicit a change in gene expression or protein function in response to phosphoryl transfer from a histidine kinase. Phosphorylation of the associated histidine kinase is regulated by detection of an environmental signal, thus linking sensing to cellular response. Recently, it has been suggested that H-NOX (Heme-nitric oxide/oxygen binding) proteins may act as nitric oxide (NO) sensors in two-component signaling systems. NO/H-NOX regulated histidine kinases have been reported, but their cognate response regulators have yet to be identified. In this work we provide biochemical characterization of a complete NO/H-NOX-regulated two-component signaling pathway in the biofilm-dwelling marine bacterium, Pseudoalteromonas atlantica. In P. atlantica, as is typical for bacteria that code for H-NOX, an hnoX gene is found in the same operon as a gene coding for a two-component signaling histidine kinase (H-NOX-associated histidine kinase; HahK). We find that HahK is capable of autophosphorylation in vitro and that NO-bound H-NOX inhibits HahK activity, implicating H-NOX as a selective NO sensor. The cognate response regulator, a protein annotated as a cyclic-di-GMP processing enzyme that we have named HarR (H-NOX-associated response regulator), was identified using bioinformatics tools. Phosphoryl transfer from HahK to HarR has been established. This report reveals the first biochemical characterization of an H-NOX-associated response regulator and contributes to a deeper understanding of NO/H-NOX signaling in bacteria.     

Aberrant Cell Division and Random FtsZ Ring Positioning in Escherichia coli cpxA* Mutants

In Escherichia coli, certain mutations in the cpxA gene (encoding a sensor kinase of a two-component signal transduction system) randomize the location of FtsZ ring assembly and dramatically affect cell division. However, deletion of the cpxRA operon, encoding the sensor kinase and its cognate regulator CpxR, has no effect on division site biogenesis. It appears that certain mutant sensor kinases (CpxA*) either exhibit hyperactivity on CpxR or extend their signalling activity to one or more noncognate response regulators involved in cell division.