The reaction center of purple bacteria contains a tightly bound cytochrome molecule which re-reduces the photo oxidized primary electron donor. Component of the photosynthetic reaction center composed of protein subunits L (PufL), M (PufM), H (PuhA) and cytochrome C (PufC). The reaction center interacts with light-harvesting antenna complex LH1. Binds 4 heme groups per subunit.