Periplasmic location of nitrous oxide reductase and its apoform in denitrifying Pseudomonas stutzeri

Immunogold labelling techniques on ultrathin sections of low temperature embedded cells yielded evidence for the periplasmic location of the respiratory enzymes N₂O reductase and nitrite reductase (cytochrome cd ₁) in Pseudomonas stutzeri strain ZoBell. Cell fractionation by spheroplast preparation and two-dimensional electrophoresis showed the absence of a membrane association of these enzymes. Immunocytochemical localization of N₂O reductase in a mutant strain deficient in the chromophore of N₂O reductase showed the gold label at the cell periphery, indicating that the copper chromophore processing takes place after export of this protein's apoform.