The quinone acceptor A 1 in photosystem I: Binding site, and comparison to Q A in purple bacteria reaction centers

Andreas Kamlowski, Brigitte Altenberg-Greulich, Arthur Van Der Est, Stephan G. Zech, Robert Bittl, Petra Fromme, Wolfgang Lubitz, Dietmar Stehlik

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

The nature of the binding site of the quinone acceptor A 1 in Photosystem I (PSI) is studied by modeling the protein and cofactor on the basis of structural data derived from the intermediate resolution 4 Å X-ray diffraction electron density map, the position and orientation of A 1 as evaluated from EPR data, and the histidine ligation of P 700 as deduced from mutation experiments. Several models are constructed within the degrees of freedom allowed by the experimental constraints. In all cases a close interaction between the A 1 headgroup and the side chain of PsaA-Trp697 (PsaB-Trp677) is found. The model is compared to the known binding site of Q A in bacterial reaction centers (bRC) in which a similar quinone-tryptophan arrangement has been established. The results are also compared for consistency with published magnetic resonance data. The influences of the protein environment on the semiquinone g-tensor and hyperfine couplings are considerably different in PSI and bRC. It is argued that this is mainly a result of differences in the hydrogen bonding to the protein, in the strength of the π-π interactions with the tryptophan, and in the protein induced asymmetry in the spin density of the respective quinone radical anion.

Original languageEnglish
Pages (from-to)8278-8287
Number of pages10
JournalJournal of Physical Chemistry B
Volume102
Issue number42
Publication statusPublished - Oct 15 1998

    Fingerprint

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Kamlowski, A., Altenberg-Greulich, B., Van Der Est, A., Zech, S. G., Bittl, R., Fromme, P., Lubitz, W., & Stehlik, D. (1998). The quinone acceptor A 1 in photosystem I: Binding site, and comparison to Q A in purple bacteria reaction centers. Journal of Physical Chemistry B, 102(42), 8278-8287.