Photosynthetic Water Oxidation in Cytochrome b559 Mutants Containing a Disrupted Heme-binding Pocket

Francisco Morais, Kristina Kühn, David H. Stewart, James Barber, Gary W Brudvig, Peter J. Nixon

Research output: Contribution to journalArticle

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Abstract

The role of cytochrome b559 in photosynthetic oxygen evolution has been investigated in three chloroplast mutants of Chlamydomonas reinhardtii, in which one of the two histidine axial ligands to the heme, provided by the α subunit, has been replaced by the residues methionine, tyrosine, and glutamine. Photosystem two complexes functional for oxygen evolution could be assembled in the methionine and tyrosine mutants up to ∼15% of wild type levels, whereas no complexes with oxygen evolution activity could be detected in the glutamine mutant. PSII supercomplexes isolated from the tyrosine and methionine mutants were as active as wild type in terms of light-saturated rates of oxygen evolution but in contrast to wild type contained no bound heme despite the presence of the α subunit. Oxygen evolution in the tyrosine and methionine mutants was, however, more sensitive to photoinactivation than the WT. Overall, these data establish unambiguously that a redox role for the heme of cytochrome b559 is not required for photosynthetic oxygen evolution. Instead, our data provide new evidence of a role for cytochrome b559 in the protection of the photosystem two complex in vivo.

Original languageEnglish
Pages (from-to)31986-31993
Number of pages8
JournalJournal of Biological Chemistry
Volume276
Issue number34
DOIs
Publication statusPublished - Aug 24 2001

Fingerprint

Heme
Oxygen
Methionine
Oxidation
Tyrosine
Water
Glutamine
Chlamydomonas reinhardtii
Chloroplasts
Histidine
Oxidation-Reduction
cytochrome b559
Ligands
Light

ASJC Scopus subject areas

  • Biochemistry

Cite this

Photosynthetic Water Oxidation in Cytochrome b559 Mutants Containing a Disrupted Heme-binding Pocket. / Morais, Francisco; Kühn, Kristina; Stewart, David H.; Barber, James; Brudvig, Gary W; Nixon, Peter J.

In: Journal of Biological Chemistry, Vol. 276, No. 34, 24.08.2001, p. 31986-31993.

Research output: Contribution to journalArticle

Morais, Francisco ; Kühn, Kristina ; Stewart, David H. ; Barber, James ; Brudvig, Gary W ; Nixon, Peter J. / Photosynthetic Water Oxidation in Cytochrome b559 Mutants Containing a Disrupted Heme-binding Pocket. In: Journal of Biological Chemistry. 2001 ; Vol. 276, No. 34. pp. 31986-31993.
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