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1z9k

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[[Image:1z9k.gif|left|200px]]
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{{STRUCTURE_1z9k| PDB=1z9k | SCENE= }}
{{STRUCTURE_1z9k| PDB=1z9k | SCENE= }}
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'''Photosynthetic Reaction Center from Rhodobacter sphaeroides'''
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===Photosynthetic Reaction Center from Rhodobacter sphaeroides===
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==Overview==
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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.
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(as it appears on PubMed at http://www.pubmed.gov), where 15895982 is the PubMed ID number.
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{{ABSTRACT_PUBMED_15895982}}
==About this Structure==
==About this Structure==
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[[Category: Alpha helix]]
[[Category: Alpha helix]]
[[Category: Membrane protein]]
[[Category: Membrane protein]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 17:21:12 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 08:28:39 2008''

Revision as of 05:28, 29 July 2008

Image:1z9k.png

Template:STRUCTURE 1z9k

Photosynthetic Reaction Center from Rhodobacter sphaeroides

Template:ABSTRACT PUBMED 15895982

About this Structure

1Z9K is a Protein complex structure of sequences from Rhodobacter sphaeroides. Full crystallographic information is available from OCA.

Reference

Design of a redox-linked active metal site: manganese bound to bacterial reaction centers at a site resembling that of photosystem II., Thielges M, Uyeda G, Camara-Artigas A, Kalman L, Williams JC, Allen JP, Biochemistry. 2005 May 24;44(20):7389-94. PMID:15895982

Page seeded by OCA on Tue Jul 29 08:28:39 2008

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