A bacteriophage-encoded J-domain protein interacts with the DnaK/Hsp70 chaperone and stabilizes the heat-shock factor σ32 of Escherichia coli.

The universally conserved J-domain proteins (JDPs) are obligate cochaperone partners of the Hsp70 (DnaK) chaperone. They stimulate Hsp70's ATPase activity, facilitate substrate delivery, and confer specific cellular localization to Hsp70. In this work, we have identified and characterized the first functional JDP protein encoded by a bacteriophage.

Characterization of Nda2, a plastoquinone-reducing type II NAD(P)H dehydrogenase in chlamydomonas chloroplasts.

Electron transfer pathways associated to oxygenic photosynthesis, including cyclic electron flow around photosystem I and chlororespiration, rely on non-photochemical reduction of plastoquinones (PQs). In higher plant chloroplasts, a bacterial-like NDH complex homologous to complex I is involved in PQ reduction, but such a complex is absent from Chlamydomonas plastids where a type II NAD(P)H dehydrogenase activity has been proposed to operate. With the aim to elucidate the nature of the enzyme-supporting non-photochemical reduction of PQs, one of the type II NAD(P)H dehydrogenases identified in the Chlamydomonas reinhardtii genome (Nda2) was produced as a recombinant protein in Escherichia coli and further characterized.

Agrobacterium tumefaciens type II NADH dehydrogenase. Characterization and interactions with bacterial and thylakoid membranes.

Type II NADH dehydrogenases (NDH-2) are monomeric enzymes that catalyse quinone reduction and allow electrons to enter the respiratory chain in different organisms including higher plant mitochondria, bacteria and yeasts. In this study, an Agrobacterium tumefaciens gene encoding a putative alternative NADH dehydrogenase (AtuNDH-2) was isolated and expressed in Escherichia coli as a (His)6-tagged protein. The purified 46 kDa protein contains FAD as a prosthetic group and oxidizes both NADH and NADPH with similar Vmax values, but with a much higher affinity for NADH than for NADPH.

Plasticity of the gene functions for DNA replication in the T4-like phages.

We have completely sequenced and annotated the genomes of several relatives of the bacteriophage T4, including three coliphages (RB43, RB49 and RB69), three Aeromonas salmonicida phages (44RR2.8t, 25 and 31) and one Aeromonas hydrophila phage (Aeh1). In addition, we have partially sequenced and annotated the T4-like genomes of coliphage RB16 (a close relative of RB43), A.

The diversity and evolution of the T4-type bacteriophages.

Recent studies suggest that viruses are the most numerous entities in the biosphere; bacteriophages, the viruses that infect Eubacteria and Archaea, constitute a substantial fraction of this population. In spite of their ubiquity, the vast majority of phages in the environment have never been studied and nothing is known about them. For the last 10 years our research has focused on an extremely widespread group of phages, the T4-type.

Snapshot of the genome of the pseudo-T-even bacteriophage RB49.

RB49 is a virulent bacteriophage that infects Escherichia coli. Its virion morphology is indistinguishable from the well-known T-even phage T4, but DNA hybridization indicated that it was phylogenetically distant from T4 and thus it was classified as a pseudo-T-even phage. To further characterize RB49, we randomly sequenced small fragments corresponding to about 20% of the approximately 170-kb genome.