Location of chloride and its possible functions in oxygen-evolving photosystem II revealed by X-ray crystallography.

Content Provider	Semantic Scholar
Author	Kawakami, Keisuke Umena, Yasufumi Kamiya, Nobuo Shen, Jian-Ren
Copyright Year	2009
Abstract	The chloride ion, Cl(-), is an essential cofactor for oxygen evolution of photosystem II (PSII) and is closely associated with the Mn(4)Ca cluster. Its detailed location and function have not been identified, however. We substituted Cl(-) with a bromide ion (Br(-)) or an iodide ion (I(-)) in PSII and analyzed the crystal structures of PSII with Br(-) and I(-) substitutions. Substitution of Cl(-) with Br(-) did not inhibit oxygen evolution, whereas substitution of Cl(-) with I(-) completely inhibited oxygen evolution, indicating the efficient replacement of Cl(-) by I(-). PSII with Br(-) and I(-) substitutions were crystallized, and their structures were analyzed. The results showed that there are 2 anion-binding sites in each PSII monomer; they are located on 2 sides of the Mn(4)Ca cluster at equal distances from the metal cluster. Anion-binding site 1 is close to the main chain of D1-Glu-333, and site 2 is close to the main chain of CP43-Glu-354; these 2 residues are coordinated directly with the Mn(4)Ca cluster. In addition, site 1 is located in the entrance of a proton exit channel. These results indicate that these 2 Cl(-) anions are required to maintain the coordination structure of the Mn(4)Ca cluster as well as the proposed proton channel, thereby keeping the oxygen-evolving complex fully active.
File Format	PDF HTM / HTML
DOI	10.1073/pnas.0812797106
PubMed reference number	19433803
Journal	Medline
Volume Number	106
Issue Number	21
Alternate Webpage(s)	http://www.pnas.org/content/106/21/8567.full.pdf
Alternate Webpage(s)	https://doi.org/10.1073/pnas.0812797106
Journal	Proceedings of the National Academy of Sciences of the United States of America
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article