1kby
Structure of Photosynthetic Reaction Center with bacteriochlorophyll-bacteriopheophytin heterodimer
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OverviewOverview
Crystals have been obtained of reaction centers of the heterodimer mutant, that has significantly different properties than wild type due to the, primary donor being formed from both a bacteriochlorophyll and, bacteriopheophytin rather than two bacteriochlorophylls as found for wild, type. The crystals belong to the trigonal space group P3(1)21 and the, structure has been refined to a resolution limit of 2.55 A with an R, factor of 19.0%. The electron density maps confirm that a primary donor, does indeed contain a bacteriopheophytin due to the His to Leu, substitution at M202 that coordinates the corresponding, bacteriochlorophyll in wild-type. Other structural changes compared to, wild type are relatively minor with the relative orientation and, positioning of the two tetrapyrroles forming the primary donor being, unchanged within the error. Compared to wild type, the only significant, alterations are small shifts of residues M196 to M206, a rotation of the, side chain of Ile M206, and the loss of a bound water molecule that in, wild-type is hydrogen-bonded to both His M202 and the bacteriochlorophyll, monomer on the active branch. Since hydrogen-bonding interactions strongly, influence the energies of tetrapyrroles, the loss of the water molecule, should result in changes in the energies of the bacteriochlorophyll, monomer that contributes to the observed functional differences with, wild-type.
About this StructureAbout this Structure
1KBY is a Protein complex structure of sequences from Rhodobacter sphaeroides with FE, CL, BCL, BPH, U10, SPO and CDL as ligands. Full crystallographic information is available from OCA.
ReferenceReference
The structure of the heterodimer reaction center from Rhodobacter sphaeroides at 2.55 a resolution., Camara-Artigas A, Magee C, Goetsch A, Allen JP, Photosynth Res. 2002;74(1):87-93. PMID:16228547
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