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A novel "four-component" two-component signal transduction mechanism regulates developmental progression in Myxococcus xanthus.

ABSTRACT: Histidine-aspartate phosphorelays are employed by two-component signal transduction family proteins to mediate responses to specific signals or stimuli in microorganisms and plants. The RedCDEF proteins constitute a novel signaling system in which four two-component proteins comprising a histidine kinase, a histidine-kinase like protein, and two response regulators function together to regulate progression through the elaborate developmental program of Myxococcus xanthus. A combination of in vivo phenotypic analyses of in-frame deletions and non-functional point mutations in each gene as well as in vitro autophosphorylation and phosphotransfer analyses of recombinant proteins indicate that the RedC histidine kinase protein autophosphorylates and donates a phosphoryl group to the single domain response regulator, RedF, to repress progression through the developmental program. To relieve this developmental repression, RedC instead phosphorylates RedD, a dual receiver response regulator protein. Surprisingly, RedD transfers the phosphoryl group to the histidine kinase-like protein RedE, which itself appears to be incapable of autophosphorylation. Phosphorylation of RedE may render RedE accessible to RedF, where it removes the phosphoryl group from RedF-P, which is otherwise an unusually stable phosphoprotein. These analyses reveal a novel "four-component" signaling mechanism that has probably arisen to temporally coordinate signals controlling the developmental program in M. xanthus. The RedCDEF signaling system provides an important example of how the inherent plasticity and modularity of the basic two-component signaling domains comprise a highly adaptable framework well suited to expansion into complex signaling mechanisms.

SUBMITTER: Jagadeesan S

PROVIDER: S-EPMC2755868 | biostudies-other | 2009 Aug

REPOSITORIES: biostudies-other

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A novel "four-component" two-component signal transduction mechanism regulates developmental progression in Myxococcus xanthus.

Jagadeesan Sakthimala S Mann Petra P Schink Christian W CW Higgs Penelope I PI

The Journal of biological chemistry 20090617 32

Histidine-aspartate phosphorelays are employed by two-component signal transduction family proteins to mediate responses to specific signals or stimuli in microorganisms and plants. The RedCDEF proteins constitute a novel signaling system in which four two-component proteins comprising a histidine kinase, a histidine-kinase like protein, and two response regulators function together to regulate progression through the elaborate developmental program of Myxococcus xanthus. A combination of in viv ...[more]

PMID: 19535336

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Project description:UnlabelledIn the bacterium Myxococcus xanthus, starvation triggers the formation of multicellular fruiting bodies containing thousands of stress-resistant spores. Recent work showed that fruiting body development is regulated by a cascade of transcriptional activators called enhancer binding proteins (EBPs). The EBP Nla6 is a key component of this cascade; it regulates the promoters of other EBP genes, including a downstream-functioning EBP gene that is crucial for sporulation. In recent expression studies, hundreds of Nla6-dependent genes were identified, suggesting that the EBP gene targets of Nla6 may be part of a much larger regulon. The goal of this study was to identify and characterize genes that belong to the Nla6 regulon. Accordingly, a direct repeat [consensus, C(C/A)ACGNNGNC] binding site for Nla6 was identified using in vitro and in vivo mutational analyses, and the sequence was subsequently used to find 40 potential developmental promoter (88 gene) targets. We showed that Nla6 binds to the promoter region of four new targets (asgE, exo, MXAN2688, and MXAN3259) in vitro and that Nla6 is important for their normal expression in vivo. Phenotypic studies indicate that all of the experimentally confirmed targets of Nla6 are primarily involved in sporulation. These targets include genes involved in transcriptional regulation, cell-cell signal production, and spore differentiation and maturation. Although sporulation occurs late in development, all of the developmental loci analyzed here show an Nla6-dependent burst in expression soon after starvation is induced. This finding suggests that Nla6 starts preparing cells for sporulation very early in the developmental process.ImportanceBacterial development yields a remarkable array of complex multicellular forms. One such form, which is commonly found in nature, is a surface-associated aggregate of cells known as a biofilm. Mature biofilms are structurally complex and contain cells that are highly resistant to antibacterial agents. When starving, the model bacterium Myxococcus xanthus forms a biofilm containing a thin mat of cells and multicellular structures that house a highly resistant cell type called a myxospore. Here, we identify the promoter binding site of the transcriptional activator Nla6, identify genes in the Nla6 regulon, and show that several of the genes in the Nla6 regulon are important for production of stress-resistant spores in starvation-induced M. xanthus biofilms.

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A novel "four-component" two-component signal transduction mechanism regulates developmental progression in Myxococcus xanthus.

Publications

A novel "four-component" two-component signal transduction mechanism regulates developmental progression in Myxococcus xanthus.

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