Site-directed mutagenesis identifies a tyrosine radical involved in the photosynthesized oxygen-evolving system

Journal Article · Fri Jan 01 04:00:00 EST 1988 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.85.2.427· OSTI ID:6143367

Debus, R J; Barry, B A; Babcock, G T; McIntosh, L

Photosynthetic oxygen evolution takes place in the thylakoid protein complex known as photosystem II. The reaction center core of this photosystem, where photochemistry occurs, is a heterodimer of homologous polypeptides called D1 and D2. Besides chlorophyll and quinone, photosystem II contains other organic cofactors, including two known as Z and D. Z transfers electrons from the site of water oxidation to the oxidized reaction center primary donor, P/sub 680//sup +/, while D /center dot//sup +/ gives rise to the dark-stable EPR spectrum known as signal II. D/center dot//sup +/ has recently been shown to be a tyrosine radical. Z is probably a second tyrosine located in a similar environment. Indirect evidence indicates that Z and D are associated with the D1 and E2 polypeptides, respectively. To identify the specific tyrosine residue corresponding to D, the authors have changed Tyr-160 of the D2 polypeptide to phenylalanine by site-directed mutagenesis of a psbD gene in the cyanobacterium Synechocystis 6803. The resulting mutant grows photosynthetically, but it lacks the EPR signal of D/center dot//sup +/. The authors conclude that D is Tyr-160 of the D2 polypeptide. They suggest that the C/sub 2/ symmetry in photosystem II extends beyond P/sub 680/ to its immediate electron donor and conclude that Z is Try-161 of the D1 polypeptide.

• Research Organization: Michigan State Univ., East Lansing (USA)
• DOE Contract Number: AC02-76ER01338
• OSTI ID: 6143367
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 85:2; ISSN PNASA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOPHYSICS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CYANOBACTERIA
DAYS LIVING RADIOISOTOPES
DNA
DNA SEQUENCING
ELECTRON SPIN RESONANCE
ELECTRON TRANSFER
HYDROXY ACIDS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MICROORGANISMS
MUTAGENESIS
NUCLEI
NUCLEIC ACIDS
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PHOTOSYNTHETIC REACTION CENTERS
RADIOISOTOPES
RESONANCE
STRUCTURAL CHEMICAL ANALYSIS
SYNTHESIS
TYROSINE