Structure of the bc1–cbb3 respiratory supercomplex from Pseudomonas aeruginosa

Significance The electrochemical proton gradient needed for ATP synthesis in cells is sustained by the coupled electron transfer and proton translocation activities of respiratory chain complexes. The respiratory chain of Pseudomonas aeruginosa is central to the organism’s pathogenicity, but is poorly understood. In P. aeruginosa the penultimate respiratory complex, cytochrome bc1, can transfer electrons to several different terminal oxidases. We demonstrate that cytochrome bc1 can form a supercomplex with multiple isoforms of cytochrome cbb3 and transfer electrons directly to them via bound cytochrome c4 and c5. The structure of the bc1–c4c5–cbb3 supercomplex suggests that this type of supercomplex may occur in other pathogenic bacteria.