Site-directed mutations of two histidine residues in the D2 protein inactivate and destabilize photosystem ii in the cyanobacterium synechocystis 6803

Willem Vermaas, John G K Williams, Charles J. Arntzen

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

Site-directed mutations were created in the cyanobacterium Synechocystis 6803 to alter specific histidine residues of the photosystem II (PS II) D2 protein. In one mutant (tyr-197), the his-197 residue was replaced by tyrosine, in another mutant (asn-214), his-214 was changed into asparagine. The tyr-197 mutant did not show any low-temperature fluorescence attributable to PS II, but contained a PSII chlorophyll-protein, CP-47, in significant quantities. Another PS II chlorophyll-protein, CP-43, was absent, as was PS II-related herbicide binding. The asn-214 mutant showed a blue-shifted low-temperature fluorescence maximum around 682 nm, but did not have a significant amount of membrane-incorporated CP-43 or CP-47. Herbicide binding was also absent in this mutant. These data indicate a very important role of the his-197 and his-214 residues in the D2 protein, and are interpreted to support the hypothesis that the D2 protein and the M subunit from the photosynthetic reaction center of purple bacteria have analogous functions. According to this hypothesis, his-197 is involved in binding of P680. and his-214 forms ligands with QA and Fe2+. In absence of a functional D2 protein, the PS II core complex appears to be destabilized as evidenced by loss of chlorophyll-proteins inthe mutants.

Original languageEnglish (US)
Pages (from-to)762-768
Number of pages7
JournalZeitschrift fur Naturforschung - Section C Journal of Biosciences
Volume42
Issue number6
DOIs
StatePublished - Jun 1 1987

Keywords

  • Cyanobacteria
  • Herbicide Binding
  • Photosynthesis
  • Photosystem II Proteins
  • Site-Directed Mutagenesis

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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