Electron-transport protein of unknown function. Binds 1 heme b (iron(II)-protoporphyrin IX) group per molecule. E(0) is about +180 mV. Monomer. Belongs to the cytochrome b562 family. In strains K / NM522 and K12 / MG1655 the cybC gene has a 26 bp deletion and lacks the first 7 amino acids. It is not translated in those strains.