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Title
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Structure of a second crystal form of Bence-Jones protein Loc: strikingly different domain associations in two crystal forms of a single protein.
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Authors
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M.Schiffer,
C.Ainsworth,
Z.B.Xu,
W.Carperos,
K.Olsen,
A.Solomon,
F.J.Stevens,
C.H.Chang.
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Ref.
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Biochemistry, 1989,
28,
4066-4072.
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PubMed id
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Abstract
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We have determined the structure of the immunoglobulin light-chain dimer Loc in
a second crystal form that was grown from distilled water. The crystal structure
was determined to 2.8-A resolution; the R factor is 0.22. The two variable
domains are related by local 2-fold axes and form an antigen binding "pocket".
The variable domain-variable domain interaction observed in this crystal form
differs from the one exhibited by the protein when crystallized from ammonium
sulfate in which the two variable domains formed a protrusion (Chang et al.,
1985). The structure attained in the distilled water crystals is similar to, but
not identical with, the one observed for the Mcg light-chain dimer in crystals
grown from ammonium sulfate. Thus, two strikingly different structures were
attained by this multisubunit protein in crystals grown under two different,
commonly used, crystallization techniques. The quaternary interactions exhibited
by the protein in the two crystal forms are sufficiently different to suggest
fundamentally different interpretations of the structural basis for the function
of this protein. This observation may have general implications regarding the
use of single crystallographic determinations for detailed identification of
structural and functional relationships. On the other hand, proteins whose
structures can be altered by manipulation of crystallization conditions may
provide useful systems for study of fundamental structural chemistry.
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