1Z9K

Photosynthetic Reaction Center from Rhodobacter sphaeroides

Summary for 1Z9K

• Entry DOI: 10.2210/pdb1z9k/pdb
• Related: 1m3x 1z9j
• Descriptor: Reaction center protein L chain, Reaction center protein M chain, Reaction center protein H chain, ... (8 entities in total)
• Functional Keywords: alpha helix, membrane protein, photosynthesis
• Biological source: Rhodobacter sphaeroides; More
• Cellular location: Cellular chromatophore membrane; Multi-pass membrane protein: P02954 P02953; Cellular chromatophore membrane; Single-pass membrane protein: P11846
• Total number of polymer chains: 3
• Total formula weight: 101073.17

Authors

Camara-Artigas, A.,Allen, J.P. (deposition date: 2005-04-02, release date: 2005-06-07, Last modification date: 2023-08-23)

Primary citation

Uyeda, G.,Camara-Artigas, A.,Williams, J.C.,Allen, J.P.
Design of a Redox-Linked Active Metal Site: Manganese Bound to Bacterial Reaction Centers at a Site Resembling That of Photosystem II
Biochemistry, 44:7389-7394, 2005

PubMed Abstract: Metals bound to proteins perform a number of crucial biological reactions, including the oxidation of water by a manganese cluster in photosystem II. Although evolutionarily related to photosystem II, bacterial reaction centers lack both a strong oxidant and a manganese cluster for mediating the multielectron and proton transfer needed for water oxidation. In this study, carboxylate residues were introduced by mutagenesis into highly oxidizing reaction centers at a site homologous to the manganese-binding site of photosystem II. In the presence of manganese, light-minus-dark difference optical spectra of reaction centers from the mutants showed a lack of the oxidized bacteriochlorophyll dimer, while the reduced primary quinone was still present, demonstrating that manganese was serving as a secondary electron donor. On the basis of these steady-state optical measurements, the mutant with the highest-affinity site had a dissociation constant of approximately 1 microM. For the highest-affinity mutant, a first-order rate with a lifetime of 12 ms was observed for the reduction of the oxidized bacteriochlorophyll dimer by the bound manganese upon exposure to light. The dependence of the amplitude of this component on manganese concentration yielded a dissociation constant of approximately 1 muM, similar to that observed in the steady-state measurements. The three-dimensional structure determined by X-ray diffraction of the mutant with the high-affinity site showed that the binding site contains a single bound manganese ion, three carboxylate groups (including two groups introduced by mutagenesis), a histidine residue, and a bound water molecule. These reaction centers illustrate the successful design of a redox active metal center in a protein complex.

PubMed: 15895982
DOI: 10.1021/bi050377n

Experimental method

X-RAY DIFFRACTION (4.6 Å)