Strontium EXAFS Reveals the Proximity of Calcium to the Manganese Cluster of Oxygen-Evolving Photosystem II.

ABSTRACT: The oxygen-evolving complex of Photosystem II (PS II) in green plants and algae contains a cluster of four manganese atoms in the active site, which catalyzes the photoinduced oxidation of water to dioxygen. Along with Mn, calcium and chloride ions are necessary cofactors for proper functioning of the complex. A key unresolved question is whether Ca is close to the Mn cluster, within about 3.5 Å. To further test and verify this finding, we substituted strontium for Ca and probed from the Sr point-of-view for any nearby Mn. Sr has been shown to replace Ca and still maintain enzyme activity (about 40% of normal rate). The extended X-ray absorption fine structure (EXAFS) of Sr-PS II probes the local environment around the Sr cofactor to detect any nearby Mn. We focused on the functional Sr by

SUBMITTER: Cinco RM 

PROVIDER: S-EPMC4139056 | biostudies-literature | 1998 Oct

REPOSITORIES: biostudies-literature