Dickeya dadantii pectic enzymes necessary for virulence are also responsible for activation of the Arabidopsis thaliana innate immune system.

Soft-rot diseases of plants attributed to Dickeya dadantii result from lysis of the plant cell wall caused by pectic enzymes released by the bacterial cell by a type II secretion system (T2SS). Arabidopsis thaliana can express several lines of defence against this bacterium. We employed bacterial mutants with defective envelope structures or secreted proteins to examine early plant defence reactions.

An extended network of genomic maintenance in the archaeon Pyrococcus abyssi highlights unexpected associations between eucaryotic homologs.

In Archaea, the proteins involved in the genetic information processing pathways, including DNA replication, transcription, and translation, share strong similarities with those of eukaryotes. Characterizations of components of the eukaryotic-type replication machinery complex provided many interesting insights into DNA replication in both domains. In contrast, DNA repair processes of hyperthermophilic archaea are less well understood and very little is known about the intertwining between DNA synthesis, repair and recombination pathways.

Modulation of the Pyrococcus abyssi NucS endonuclease activity by replication clamp at functional and structural levels.

Pyrococcus abyssi NucS is the founding member of a new family of structure-specific DNA endonucleases that interact with the replication clamp proliferating cell nuclear antigen (PCNA). Using a combination of small angle x-ray scattering and surface plasmon resonance analyses, we demonstrate the formation of a stable complex in solution, in which one molecule of the PabNucS homodimer binds to the outside surface of the PabPCNA homotrimer. Using fluorescent labels, PCNA is shown to increase the binding affinity of NucS toward single-strand/double-strand junctions on 5' and 3' flaps, as well as to modulate the cleavage specificity on the branched DNA structures.

Structure and function of a novel endonuclease acting on branched DNA substrates.

Branched DNA structures that occur during DNA repair and recombination must be efficiently processed by structure-specific endonucleases in order to avoid cell death. In the present paper, we summarize our screen for new interaction partners for the archaeal replication clamp that led to the functional characterization of a novel endonuclease family, dubbed NucS. Structural analyses of Pyrococcus abyssi NucS revealed an unexpected binding site for ssDNA (single-stranded DNA) that directs, together with the replication clamp, the nuclease activity of this protein towards ssDNA-dsDNA (double-stranded DNA) junctions.

The crystal structure of pectate lyase peli from soft rot pathogen Erwinia chrysanthemi in complex with its substrate.

The crystallographic structure of the family 3 polysaccharide lyase (PL-3) PelI from Erwinia chrysanthemi has been solved to 1.45 A resolution. It consists of an N-terminal domain harboring a fibronectin type III fold linked to a catalytic domain displaying a parallel beta-helix topology.

Structure of a d(TGGGGT) quadruplex crystallized in the presence of Li+ ions.

A parallel 5'-d(TGGGGT)-3' quadruplex was formed in Na(+) solution and crystallized using lithium sulfate as the main precipitating agent. The X-ray structure was determined to 1.5 A resolution in space group P2(1) by molecular replacement.