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Title
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Determination of the solution structures of domains II and III of protein G from Streptococcus by 1H nuclear magnetic resonance.
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Authors
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L.Y.Lian,
J.P.Derrick,
M.J.Sutcliffe,
J.C.Yang,
G.C.Roberts.
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Ref.
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J Mol Biol, 1992,
228,
1219-1234.
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PubMed id
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Abstract
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We have used 1H nuclear magnetic resonance spectroscopy to determine the
solution structures of two small (61 and 64 residue) immunoglobulin G
(IgG)-binding domains from protein G, a cell-surface protein from Streptococcus
strain G148. The two domains differ in sequence by four amino acid
substitutions, and differ in their affinity for some subclasses of IgG. The
structure of domain II was determined using a total of 478 distance restraints,
31 phi and 9 chi 1 dihedral angle restraints; that of domain III was determined
using a total of 445 distance restraints, 31 phi and 9 chi 1 dihedral angle
restraints. A protocol which involved distance geometry, simulated annealing and
restrained molecular dynamics was used to determine ensembles of 40 structures
consistent with these restraints. The structures are found to consist of an
alpha-helix packed against a four-stranded antiparallel-parallel-antiparallel
beta-sheet. The structures of the two domains are compared to each other and to
the reported structure of a similar domain from a protein G from a different
strain of Streptococcus. We conclude that the difference in affinity of domains
II and III for IgG is due to local changes in amino acid side-chains, rather
than a more extensive change in conformation, suggesting that one or more of the
residues which differ between them are directly involved in interaction with IgG.
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