1K6N: E(L212)a,D(L213)a Double Mutant Structure Of Photosynthetic Reaction Center From Rhodobacter Sphaeroides

Citation:
Abstract
We report on the unexpected structural changes caused by substitution of acidic amino acids in the Q(B) binding pocket of the bacterial photosynthetic reaction center by alanines. The mutations targeted key residues L212Glu and L213Asp of this transmembrane protein-cofactor complex. The amino acid substitutions in the L212Ala-L213Ala mutant reaction center ("AA") were known to affect the delivery of protons after the light-induced generation of Q(B)(-), which renders the AA strain incapable of photosynthetic growth. The AA structure not only revealed side chain rearrangements but also showed movement of the main chain segments that are contiguous with the mutation sites. The alanine substitutions caused an expansion of the cavity rather than its collapse. In addition, Q(B) is found mainly in the binding site that is proximal to the iron-ligand complex (closest to Q(A)) as opposed to its distal binding site (furthest from Q(A)) in the structure of the wild-type reaction center. The observed rearrangements in the structure of the AA reaction center establish a new balance between charged residues of an interactive network near Q(B). This structurally and electrostatically altered complex forms the basis for future understanding of the structural basis for proton transfer in active reaction centers which retain the alanine substitutions but carry a distant compensatory mutation.
PDB ID: 1K6NDownload
MMDB ID: 20140
PDB Deposition Date: 2001/10/16
Updated in MMDB: 2012/12
Experimental Method:
x-ray diffraction
Resolution: 3.1  Å
Source Organism:
Similar Structures:
Biological Unit for 1K6N: trimeric; determined by author and by software (PISA)
Molecular Components in 1K6N
Label Count Molecule
Proteins (3 molecules)
1
Photosynthetic Reaction Center L Subunit
Molecule annotation
1
Photosynthetic Reaction Center M Subunit
Molecule annotation
1
Photosynthetic Reaction Center H Subunit
Molecule annotation
Chemicals (15 molecules)
1
4
2
2
3
2
4
4
5
1
6
1
7
1
* Click molecule labels to explore molecular sequence information.

Citing MMDB
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