High-field 2H-Mims-ENDOR spectroscopy on PSII single crystals: hydrogen bonding of YD*.
Hydrogen bonds are key determinants for protein structures and the fine-tuning of active-site properties. For example, they are responsible for the redox potential variability of protein-imbedded chromophores. By applying high-field (94 GHz) Mims-ENDOR spectroscopy on deuterium-exchanged frozen-solution samples and single crystals of photosystem II from Th. elongatus, we identified the hydrogen-bonding partner of the tyrosyl radical D2-Tyr160, Y(D)*, directly by the strength and orientation of the deuterium hyperfine coupling as D2-His189, that is, without relying on the disappearance of a hyperfine coupling interaction upon deletion of D2-His189. No indications for additional hydrogen bonds can be found in the spectra, thereby eliminating hypotheses about a water network as hydrogen-binding partner of Y(D)*.
Kessen
Sven
S
Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
Teutloff
Christian
C
Kern
Jan
J
Zouni
Athina
A
Bittl
Robert
R
D020134:Catalytic Domain; D003903:Deuterium / Q000737:chemistry; D041961:Deuterium Exchange Measurement; D004578:Electron Spin Resonance Spectroscopy; D006860:Hydrogen Bonding; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry
D045332:Photosystem II Protein Complex; C066447:tyrosyl radical Y(D); D014443:Tyrosine; D003903:Deuterium