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Title
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Crystallographic analysis of ribulose 1,5-bisphosphate carboxylase from spinach at 2.4 A resolution. Subunit interactions and active site.
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Authors
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S.Knight,
I.Andersson,
C.I.Brändén.
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Ref.
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J Mol Biol, 1990,
215,
113-160.
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PubMed id
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Abstract
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The X-ray structure of the quaternary complex of ribulose 1,5-bisphosphate
carboxylase/oxygenase from spinach with CO2, Mg2+ and a reaction-intermediate
analogue (CABP) has been determined and refined at 2.4 A resolution. Cyclic
non-crystallographic symmetry averaging around the molecular 4-fold axis and
phase combination were used to improve the initial multiple isomorphous
replacement phases. A model composed of one large subunit and one small subunit
was built in the resulting electron density map, which was of excellent quality.
Application of the local symmetry gave an initial model of the L8S8 molecule
with a crystallographic R-value of 0.43. Refinement of this initial model was
performed by a combination of conventional least-squares energy refinement and
molecular dynamics simulation using the XPLOR program. Three rounds of
refinement, interspersed with manual rebuilding at the graphics display,
resulted in a model containing all of the 123 amino acid residues in the small
subunit, and 467 of the 475 residues in the large subunit. The R-value for this
model is 0.24, with relatively small deviations from ideal stereochemistry.
Subunit interactions in the L8S8 molecule have been analysed and are described.
The interface areas between the subunits are extensive, and bury almost half of
the accessible surface areas of both the large and the small subunit. A number
of conserved interaction areas that may be of functional significance have been
identified and are described, and biochemical and mutagenesis data are discussed
in the structural framework of the model.
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