Chlorophyll and cytochrome b-559 content of the photochemical reaction center of photosystem II

Abstract

Photosystem II reaction centers comprised of the D1, D2 and cytochrome b-559 polypeptides were isolated from well-defined oxygen-evolving reaction center preparations using either a combination of LiClO4 and dodecylmaltoside, or Triton X-100 alone. Yields of chlorophyll and cytochrome b-559 for both preparative methods were compared, and pigment contents were compared based on 2.0 b-559 per reaction center, a standard derived from photosystem II components found in the starting material. Results obtained with dodecylmaltoside suggest that the reaction center of photosystem II binds 10-12 Chl a along with 2 Cyt b-559 molecules. Reaction centers prepared with Triton X-100 bind about 8 Chl a per 2 Cyt b-559 molecules, a finding which indicates that Triton X-100 extracts pigments from the reaction center polypeptides. Our results contradict the widely held notion that the pigment binding properties of the photosystem II reaction center are similar to those of the bacterial reaction center.