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Title
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The use of pseudosymmetry in the rotation function of gamma IVa-crystallin.
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Authors
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H.E.White,
H.P.Driessen,
C.Slingsby,
D.S.Moss,
W.G.Turnell,
P.F.Lindley.
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Ref.
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Acta Crystallogr B, 1988,
44,
172-178.
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PubMed id
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Abstract
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Bovine lens gamma IVa-crystallin crystallizes in space group C222(1) with cell
dimensions a = 35.1, b = 46.2, c = 186.2 A, and contains one molecule in the
asymmetric unit. The structure was determined at 3.0 A resolution using
cross-rotation functions and R-factor searches with the bovine lens protein
gamma II-crystallin as the model structure. The rotation function appears to be
very sensitive to the resolution range and type of coefficient employed; the use
of normalized structure-factor amplitudes gave the best results. The potential
problem of a pseudo solution due to an internal pseudo-twofold axis was put to
advantage by aligning this axis parallel to z. The results of the R-factor
search were well defined. The molecular replacement solution was improved by
rigid-body least-squares refinement, initially of the whole molecule, then for
the two domains. The R factor at this stage was 39.4% at 2.3-10.0 A. The gamma
IVa structure has an even higher internal symmetry than gamma II, since the two
domains are related by a rotation around the pseudo-twofold axis of 178.7
degrees as compared with 176.2 degrees for gamma II.
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