| Literature DB >> 26083545 |
Paul H Oyala1, Troy A Stich1, Richard J Debus2, R David Britt1.
Abstract
High-resolution X-ray structures of photosystem II reveal several potential substrate binding sites at the water-oxidizing/oxygen-evolving 4MnCa cluster. Aspartate-61 of the D1 protein hydrogen bonds with one such water (W1), which is bound to the dangler Mn4A of the oxygen-evolving complex. Comparison of pulse EPR spectra of (14)NH3 and (15)NH3 bound to wild-type Synechocystis PSII and a D1-D61A mutant lacking this hydrogen-bonding interaction demonstrates that ammonia binds as a terminal NH3 at this dangler Mn4A site and not as a partially deprotonated bridge between two metal centers. The implications of this finding on identifying the binding sites of the substrate and the subsequent mechanism of dioxygen formation are discussed.Entities:
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Year: 2015 PMID： 26083545 DOI： 10.1021/jacs.5b04768
Source DB: PubMed Journal: J Am Chem Soc ISSN： 0002-7863 Impact factor: 15.419