The modification of atrazine binding by the redox state of the endogenous high-spin iron and by specific proteolytic enzymes in Photosystem II membrane fragments and intact thylakoids

G. Renger, R. Fromme, R. Hagemann

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Atrazine-binding properties reflecting the fine structure of the binding niche within the 32 kDa polypeptide, D1, were analyzed in thylakoids and Photosystem II membrane fragments from spinach as a function of two parameters: (i) the redox state of the endogenous iron located between QA and QB at the Photosystem II acceptor side, and (ii) proteolytic degradation by the specifically acting enzymes trypsin, glutaminic acid-specific, lysine-specific and arginine-specific proteinases. It was found (a) Fe2+-oxidation by K3[Fe(CN)6] significantly reduces atrazine binding in Photosystem II membrane fragments. The K3[Fe(CN)6] effect exhibits a marked pH dependence attributable to different percentages of Fe3+ formation. Thylakoids hardly show any modification of atrazine binding by K3[Fe(CN)6]; (b) proteolytic enzymes which are expected to interact with specific sites of the stroma-exposed loop between transmembrane helices IV and V of polypeptide D1 affect the atrzine-binding properties quite differently. The protective action of CaCl2 to proteolytic degradation markedly depends on the nature of the enzyme used; (c) the degradation of the atrazine binding by a lysine-specific proteinase in samples from spinach, containing a lysine-free D1 polypeptide, is largely retarded if the atrazine-binding sites are occupied during the proteolytic treatment. The mechanistic implications of these findings are discussed.

Original languageEnglish (US)
Pages (from-to)173-183
Number of pages11
JournalBBA - Bioenergetics
Issue number2
StatePublished - Sep 14 1988



  • (Spinach thylakoid)
  • Atrazing binding
  • Iron redox state
  • Photosystem II
  • Proteinase

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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