Genetic probes of structure/function relationships in the Q{sub B} binding site of the photosynthetic reaction center

Technical Report · Tue Jun 25 04:00:00 EDT 1991

DOI:https://doi.org/10.2172/10148981· OSTI ID:10148981

Hanson, D K; Tiede, D M; Nance, S L; Chang, Chong-Hwan; Schiffer, M

In photosynthetic reaction centers, a quinone molecule, Q{sub B}, is the terminal acceptor in light-induced electron transfer. The crystal structure of the reaction center implicates the protonatable amiho acid residues L212Glu and L213Asp in the binding of Q{sub B} to the reaction center and in proton transfer to the anionic forms of Q{sub B} generated by electron transfer from Q{sub A}. Here we report the construction of the double mutant L212Ala-L213Ala by site-specific mutagenesis, and the isolation and preliminary biophysical characterization of revertant and suppressor strains that have regained the ability to grow under photosynthetic conditions. Our results show that neither L212Glu nor L213Asp is essential for efficient light-induced electron or proton transfer in Rhodobacter capsulatus and that second-site mutations, located within the QB binding pocket or at a more distant site, can compensate for mutations at L212 and L213. Acquisition of a single negatively charged residue (at position L213, or on the other side of the binding pocket at position L225) or loss of a positively charged residue (at position M231) is sufficient to restore activity to the complex.

• Research Organization: Argonne National Lab., IL (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States); Public Health Service, Washington, DC (United States)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 10148981
• Report Number(s): ANL/BIM/PP--71996; ON: DE94011490; CNN: Grant GM36598
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505
550200
59 BASIC BIOLOGICAL SCIENCES
AMINO ACID SEQUENCE
BIOCHEMICAL REACTION KINETICS
BIOCHEMISTRY
BIOELECTRICITY
ELECTRON TRANSFER
GENETIC ENGINEERING
MEMBRANE PROTEINS
PHOTOCHEMICAL, PHOTOBIOLOGICAL, AND THERMOCHEMICAL CONVERSION
PHOTOSYNTHETIC REACTION CENTERS
PROTEIN ENGINEERING
PROTEIN STRUCTURE
SPECIES DIVERSITY
UBIQUINONE