Studies on the functional mechanism of system II herbicides in isolated chloroplasts

G. R. Renger, R. H. Hagemann, W. F.J. Vermaas

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

The effect of specific proteolytic enzymes on variable fluorescence, p-benzoquinone-m ediated oxygen evolution, PS II herbicide (atrazine and brom oxynil) binding, and protein degradation has been analyzed in isolated class II pea chloroplasts. It was found that: 1. Trypsin and a lysine-specific protease effectively reduce the m axim um chlorophyll-a fluorescence yield, whereas the initial fluorescence remains alm ost constant. At the sam e number of enzymatic activity units both proteases have practically the sam e effect. 2 Trypsin and a lysine-specific protease inhibit the/»-benzoquinone-m ediated flash-induced oxygen evolution with trypsin being markedly more effective at the same number of activity units of both enzymes. Unstacked thylakoids exhibit a higher sensitivity to proteolytic degradation by both enzymes. 3. Trypsin and a lysine-specific protease reduce the binding capacity of [14C]atrazine, but enhance that of [14C]bromoxynil (at long incubation tim es trypsin treatment also impairs bromoxynil binding). At the same specific activity a markedly longer treatment is required for the lysine-specific protease in order to achieve the same degree of m odification as with trypsin. 4. Trypsin was found to attack the rapidly-turned-over 32 kD a-protein severely, whereas the lysine-specific protease does not modify this polypeptide. On the other hand, the lysine-specific protease attacks the light harvesting com plex II. 5. Under our experimental conditions an arginine-specific protease did not affect chlorophyll-a fluorescence yield, p-benzoquinone-mediated oxygen evolution, herbicide binding and the polypeptide pattern. Based on these results a mechanism is proposed in which an as yet unidentified polypeptide with exposable lysine residues, as well as the lysine-free “QB-protein” regulate the electrontransfer from QA to QB and are involved in herbicide binding.

Original languageEnglish (US)
Pages (from-to)362-367
Number of pages6
JournalZeitschrift fur Naturforschung - Section C Journal of Biosciences
Volume39
Issue number5
DOIs
StatePublished - May 1 1984
Externally publishedYes

Keywords

  • Chloroplasts, Proteolytic Enzymes
  • Fluorescence
  • Herbicide Binding
  • Oxygen Evolution

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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