Pseudomonas pseudoalcaligenes KF707 grown with biphenyl expresses a cytochrome caa3 oxidase that uses cytochrome c4 as electron donor.

Combining peroxidase activity-based heme staining (TMBZ/SDS/PAGE) with mass spectrometry analyses (Nano LC-MS/MS) of protein extracts from wild-type and appropriate mutants, we provide evidence that the polychlorinated biphenyl degrader Pseudomonas pseudoalcaligenes KF707 primarily expresses a caa3 -type cytochrome c oxidase (caa3 -Cox) using cytochrome (cyt) c4 as an electron donor in cells grown with biphenyl versus glucose as the sole carbon source. Homology modeling of KF707 caa3 -Cox using the three-dimensional structure of that from Thermus thermophilus highlights multiple similarities and differences between the proton channels in subunit I of the aa3 - and caa3 -Cox of Paracoccus and Thermus spp., respectively. To our knowledge, this is the first report demonstrating the presence of a caa3 -Cox using cyt c4 as an electron donor in a Pseudomonas species.