A single subunit P-700 reaction center of the thermophilic cyanobacterium Mastigoclauds laminosus

The isolation and characterization of a single subunit Photosystem I reaction center of the thermophilic cyanobacterium Mastigocladus laminosus is described. The subunit isolated in 0.1% SDS is fully active in P-700 bleaching and oxidizes cytochrome c in the light. Depending on denaturing conditions, the protein appears on SDS-PAGE in the 70 kDa or 50 kDa region and contains bound chlorophyll in both forms. The 70 kDa form shows all the activities of an intact reaction center.