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Three cdg operons control cellular turnover of cyclic di-GMP in Acetobacter xylinum: genetic organization and occurrence of conserved domains in isoenzymes.

ABSTRACT: Cyclic di-GMP (c-di-GMP) is the specific nucleotide regulator of beta-1,4-glucan (cellulose) synthase in Acetobacter xylinum. The enzymes controlling turnover of c-di-GMP are diguanylate cyclase (DGC), which catalyzes its formation, and phosphodiesterase A (PDEA), which catalyzes its degradation. Following biochemical purification of DGC and PDEA, genes encoding isoforms of these enzymes have been isolated and found to be located on three distinct yet highly homologous operons for cyclic diguanylate, cdg1, cdg2, and cdg3. Within each cdg operon, a pdeA gene lies upstream of a dgc gene. cdg1 contains two additional flanking genes, cdg1a and cdg1d. cdg1a encodes a putative transcriptional activator, similar to AadR of Rhodopseudomonas palustris and FixK proteins of rhizobia. The deduced DGC and PDEA proteins have an identical motif structure of two lengthy domains in their C-terminal regions. These domains are also present in numerous bacterial proteins of undefined function. The N termini of the DGC and PDEA deduced proteins contain putative oxygen-sensing domains, based on similarity to domains on bacterial NifL and FixL proteins, respectively. Genetic disruption analyses demonstrated a physiological hierarchy among the cdg operons, such that cdg1 contributes 80% of cellular DGC and PDEA activities and cdg2 and cdg3 contribute 15 and 5%, respectively. Disruption of dgc genes markedly reduced in vivo cellulose production, demonstrating that c-di-GMP controls this process.

SUBMITTER: Tal R

PROVIDER: S-EPMC107450 | biostudies-literature | 1998 Sep

REPOSITORIES: biostudies-literature

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Three cdg operons control cellular turnover of cyclic di-GMP in Acetobacter xylinum: genetic organization and occurrence of conserved domains in isoenzymes.

Tal R R Wong H C HC Calhoon R R Gelfand D D Fear A L AL Volman G G Mayer R R Ross P P Amikam D D Weinhouse H H Cohen A A Sapir S S Ohana P P Benziman M M

Journal of bacteriology 19980901 17

Cyclic di-GMP (c-di-GMP) is the specific nucleotide regulator of beta-1,4-glucan (cellulose) synthase in Acetobacter xylinum. The enzymes controlling turnover of c-di-GMP are diguanylate cyclase (DGC), which catalyzes its formation, and phosphodiesterase A (PDEA), which catalyzes its degradation. Following biochemical purification of DGC and PDEA, genes encoding isoforms of these enzymes have been isolated and found to be located on three distinct yet highly homologous operons for cyclic diguany ...[more]

PMID: 9721278

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Project description:UnlabelledMicroorganisms use a variety of metabolites to respond to external stimuli, including second messengers that amplify primary signals and elicit biochemical changes in a cell. Levels of the second messenger cyclic dimeric GMP (c-di-GMP) are regulated by a variety of environmental stimuli and play a critical role in regulating cellular processes such as biofilm formation and cellular motility. Cyclic di-GMP signaling systems have been largely characterized in pathogenic bacteria; however, proteins that can impact the synthesis or degradation of c-di-GMP are prominent in cyanobacterial species and yet remain largely underexplored. In cyanobacteria, many putative c-di-GMP synthesis or degradation domains are found in genes that also harbor light-responsive signal input domains, suggesting that light is an important signal for altering c-di-GMP homeostasis. Indeed, c-di-GMP-associated domains are often the second most common output domain in photoreceptors-outnumbered only by a histidine kinase output domain. Cyanobacteria differ from other bacteria regarding the number and types of photoreceptor domains associated with c-di-GMP domains. Due to the widespread distribution of c-di-GMP domains in cyanobacteria, we investigated the evolutionary origin of a subset of genes. Phylogenetic analyses showed that c-di-GMP signaling systems were present early in cyanobacteria and c-di-GMP genes were both vertically and horizontally inherited during their evolution. Finally, we compared intracellular levels of c-di-GMP in two cyanobacterial species under different light qualities, confirming that light is an important factor for regulating this second messenger in vivo.ImportanceThis study shows that many proteins containing cyclic dimeric GMP (c-di-GMP)-regulatory domains in cyanobacteria are associated with photoreceptor domains. Although the functional roles of c-di-GMP domain-containing proteins in cyanobacteria are only beginning to emerge, the abundance of these multidomain proteins in cyanobacteria that occupy diverse habitats ranging from freshwater to marine to soil environments suggests an important role for the regulation of c-di-GMP in these organisms. Indeed, we showed that light distinctly regulates c-di-GMP levels in Fremyella diplosiphon and Synechocystis sp. strain PCC6803. Our findings are consistent with the occurrence of c-di-GMP domains based on evolutionary origin and as an adaptation to specific habitat characteristics. Phylogenetic analyses of these domains clearly separate two distinctive clades, one composed of domains belonging predominantly to cyanobacteria and the other belonging to a mix of cyanobacteria and other bacteria. We further demonstrate that in cyanobacteria the acquisition of c-di-GMP signaling domains occurred both vertically and horizontally.

Dataset Information

Three cdg operons control cellular turnover of cyclic di-GMP in Acetobacter xylinum: genetic organization and occurrence of conserved domains in isoenzymes.

Publications

Three cdg operons control cellular turnover of cyclic di-GMP in Acetobacter xylinum: genetic organization and occurrence of conserved domains in isoenzymes.

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