Disruption of the Pseudomonas aeruginosa dipZ gene, encoding a putative protein-disulfide reductase, leads to partial pleiotropic deficiency in c-type cytochrome biogenesis.
The Pseudomonas aeruginosa dipZ gene has been cloned and sequenced. Whereas disruption of Escherichia coli dipZ (dsbD), the hydrophilic C-terminal domain of which has been deduced to be periplasmic and to function as a protein-disulfide reductase, leads to the absence of c-type cytochromes, disruption of P. aeruginosa dipZ attenuated, but did not abolish, holo-c-type cytochrome biosynthesis. Comparison of the P. aeruginosa DipZ sequence with three other DipZ sequences indicated that there are not only two conserved cysteine residues in the C-terminal hydrophilic domain, but also two more in the central highly hydrophobic domain. The latter would be located toward the centre of two of the eight membrane-spanning alpha-helices predicted to compose the hydrophobic central domain of DipZ. Both these cysteine residues, plus other transmembrane helix residues, notably prolines and glycines, are also conserved in a group of membrane proteins, related to Bacillus subtilis CcdA, which lack the N- and C-terminal hydrophilic domains of the DipZ proteins. It is proposed that DipZ of P. aeruginosa and other organisms transfers reducing power from the cytoplasm to the periplasm through reduction and reoxidation of an intramembrane disulfide bond, or other mechanism involving these cysteine residues, and that this function can also be performed by B. subtilis CcdA and other CcdA-like proteins. The failure of dipZ disruption to abolish c-type cytochrome synthesis in P. aeruginosa suggests that, in contrast to the situation in E. coli, the absence of DipZ can be compensated for by one or more other proteins, for example a CcdA-like protein acting in tandem with one or more thioredoxin-like proteins.
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M Dudley
MD
The Oxford Centre for Molecular Sciences, New Chemistry Building, South Parks Road, Oxford OX1 3QT, UK.|Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
Saunders
Neil F W
NFW
Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
Ferguson
Stuart J
SJ
Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.|The Oxford Centre for Molecular Sciences, New Chemistry Building, South Parks Road, Oxford OX1 3QT, UK.
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D003574:Cytochrome c Group / Q000096:biosynthesis; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D018390:Gene Targeting; D005798:Genes, Bacterial; D006193:Haemophilus influenzae / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009344:Neisseria gonorrhoeae / Q000235:genetics; D016366:Open Reading Frames; D010088:Oxidoreductases; D010641:Phenotype; D011490:Protein Disulfide Reductase (Glutathione) / Q000235:genetics*; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000378:metabolism*; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013879:Thioredoxins / Q000235:genetics
D001426:Bacterial Proteins; C104882:CcdA protein, Bacillus; D003574:Cytochrome c Group; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D013879:Thioredoxins; D010088:Oxidoreductases; C094848:DsbD electron transport protein, E coli; D011490:Protein Disulfide Reductase (Glutathione)