Cell cycle-dependent dynamic localization of a bacterial response regulator with a novel di-guanylate cyclase output domain

Abstract

Pole development is coordinated with the Caulobacter crescentus cell cycle by two-component signaling proteins. We show that an unusual response regulator, PleD, is required for polar differentiation and is sequestered to the cell pole only when it is activated by phosphorylation. Dynamic localization of PleD to the cell pole provides a mechanism to temporally and spatially control the signaling output of PleD during development. Targeting of PleD to the cell pole is coupled to the activation of a C-terminal guanylate cyclase domain, which catalyzes the synthesis of cyclic di-guanosine monophosphate. We propose that the local action of this novel-type guanylate cyclase might constitute a general regulatory principle in bacterial growth and development. During developmental transitions, localized changes of cellular morphology are mediated by adaptation in levels and arrangement of proteins. Temporal and spatial control often relies on the timed synthesis or activation of transcriptional regulators and on the establishment of gradients through the compartmentalization of signaling complexes. Although the regulatory mechanisms of gene expression are relatively well understood, it is often not clear how morphogenetic changes are controlled and coordinated locally. In prokaryotes, the major paradigm for signal transduction is the two-component regulatory system (Parkinson and Kofoid 1992). On signal input, the first component, a sensor kinase, autophosphorylates on a histidine residue. The second component, a soluble response regulator, often functions as a transcriptional regulator. Its phosphorylation by the cognate histidine kinase on a conserved aspartate residue in the N-terminal receiver domain usually results in increased DNA binding affinity (Parkinson and Kofoid 1992). Here we present evidence that a novel-type response regulator acts at a distinct subcellular site where it contributes to local changes in cell morphology through the production of a novel signaling molecule.The unicellular bacterium Caulobacter crescentus goes through an obligate developmental transition that allows it to switch between a sessile, adhesive, and a motile, planktonic cell during its cell cycle. As a consequence, cell poles are continuously remodeled during cell differentiation to facilitate assembly and removal of motility and surface adherence organelles at the right time and in the correct order. Asymmetry is established in the predivisional cell with a single flagellum, a chemotaxis machinery, and pili being assembled at one pole, whereas the opposite pole consists of a stalk and an adhesive organelle, the holdfast (Fig. 1). As a result, division generates two cell types with distinct properties: a surface-attached stalked cell and a motile swarmer cell. The swarmer progeny first differentiates into a stalked cell before it initiates DNA replication and cell division. During this transition the pili retract, flagella are released, and the adhesive organelles are synthesized at the same pole. Here we investigate the function...

The structure–function relationship of WspR, a Pseudomonas fluorescens response regulator with a GGDEF output domain

“…Although the biological pathways through which c-di-GMP regulates persistence, cell aggregation and the switch to the commensal lifestyle are currently poorly understood, the proteins responsible for c-di-GMP synthesis and degradation have been determined and, at least partially, characterized. Bacterial diguanylate cyclase (DGC) activity is found in GGDEF domain-containing proteins (Paul et al, 2004;Ryjenkov et al, 2005;Hickman et al, 2005;Kulesekara et al, 2006), whilst EAL domain-containing proteins have been shown to have c-di-GMP-specific phosphodiesterase (PDE) activity (Bobrov et al, 2005;Christen et al, 2005;Schmidt et al, 2005;Kulesekara et al, 2006).…”

“…Despite the publication of much biological data concerning GGDEF domains, biochemical demonstration of DGC activity (Paul et al, 2004;Ryjenkov et al, 2005), and the solution of the crystal structure of the GGDEF response regulator PleD (Chan et al, 2004), detailed structurefunction analyses of GGDEF proteins are relatively scarce. Christen et al (2006) have analysed the site of c-di-GMP product inhibition (the 'I site') for the Caulobacter crescentus enzymes PleD and DgcA.…”

“…For example, PleD controls the onset of motility during the C. crescentus cell cycle (Aldridge et al, 2003;Paul et al, 2004). In Pseudomonas aeruginosa, autoaggregation is controlled by the GGDEF response regulator WspR (D'Argenio et al, 2002;Hickman et al, 2005), and twitching motility by FimX, which contains GGDEF and EAL domains (Huang et al, 2003;Kazmierczak et al, 2006).…”

Shewanella oneidensis MR-1 Sensory Box Protein Involved in Aerobic and Anoxic Growth

“…The two domains are thought to interact with cyclic-diguanosine monophosphate (c-di-GMP), and c-di-GMP was recently proposed to be a global secondary messenger involved in regulating cell-cell and cell-surface interactions (9). The GGDEF domain was recently shown to be associated with the synthesis of c-di-GMP via diguanylate cyclase (DGC) and the EAL domain to contain phosphodiesterase (PDE) activity in Yersinia, Caulobacter, and Salmonella (9,16,27,24,38) and more recently in Shewanella (54). In addition, the involvement of DGC and PDE domains in cell metabolism and cell behavior has recently been shown in Burkholderia, Xanthomonas, Streptococcus, Vibrio, and Pseudomonas (for examples, see references 5 and 30).…”

“…The SO3389 ORF also contains putative GGDEF and EAL domains (originally named for the conserved amino acid residues) (9,24,38). The two domains are thought to interact with cyclic-diguanosine monophosphate (c-di-GMP), and c-di-GMP was recently proposed to be a global secondary messenger involved in regulating cell-cell and cell-surface interactions (9).…”