Glycerol stabilizes oxygen evolution and maintains binding of a 9 kDa polypeptide in photosystem II particles from the cyanobacterium, <i>Phormidium laminosum</i>

Abstract

High concentrations of glycerol (⩾20% ) stabilize oxygen evolution in photosystem (PS) II particles from the thermophilic cyanobacterium, Phormidium laminosum . Treating PS II particles with lower glycerol concentrations inhibits activity and, in parallel, detaches a 9 kDa polypeptide from PS II. These results suggest that the 9 kDa polypeptide is essential for PS II activity, and that it is bound to PS II primarily by hydrophobic interactions that are strengthened in vitro by glycerol. The 9 kDa polypeptide is distinct from cytochrome b ‐559 and does not appear to be associated with manganese or with the calcium or chloride requirements for oxygen evolution.