Genetic probes of structure/function relationships in the Q{sub B} binding site of the photosynthetic reaction center
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. (ANL), Argonne, 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
- Resource Relation:
- Other Information: PBD: 25 Jun 1991
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
14 SOLAR ENERGY
PHOTOSYNTHETIC REACTION CENTERS
PROTEIN ENGINEERING
BIOCHEMICAL REACTION KINETICS
ELECTRON TRANSFER
UBIQUINONE
MEMBRANE PROTEINS
BIOELECTRICITY
SPECIES DIVERSITY
GENETIC ENGINEERING
AMINO ACID SEQUENCE
PROTEIN STRUCTURE
550200
140505
BIOCHEMISTRY
PHOTOCHEMICAL, PHOTOBIOLOGICAL, AND THERMOCHEMICAL CONVERSION