The reaction center of purple bacteria contains a tightly bound cytochrome molecule which re-reduces the photo oxidized primary electron donor. E(0) is -60 mV for heme 1. E(0) is +320 mV for heme 2. E(0) is +380 mV for heme 3. E(0) is +15 mV for heme 4. Component of the photosynthetic reaction center composed of protein subunits L (PufL), M (PufM), H (PuhA) and cytochrome C (PufC). Binds 4 heme groups per subunit. After the signal sequence is removed, the N-terminal cysteine is modified to form a diacylglyceride thioether, but the alpha-amino group is free and is not N-palmitoylated. Lack of photosynthesis.