C-type cytochrome. Part of the cbb3-type cytochrome c oxidase complex. CcoP subunit is required for transferring electrons from donor cytochrome c via its heme groups to CcoO subunit. From there, electrons are shuttled to the catalytic binuclear center of CcoN subunit where oxygen reduction takes place. The complex also functions as a proton pump. Binds 2 heme C groups per subunit. Energy metabolism; oxidative phosphorylation. Component of the cbb3-type cytochrome c oxidase at least composed of CcoN, CcoO, CcoQ and CcoP. Interacts with CcoQ. Belongs to the CcoP / FixP family.