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PDBsum entry 4hb1
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Designed helical bundle
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PDB id
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4hb1
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References listed in PDB file
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Key reference
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Title
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A designed four helix bundle protein with native-Like structure.
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Authors
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C.E.Schafmeister,
S.L.Laporte,
L.J.Miercke,
R.M.Stroud.
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Ref.
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Nat Struct Biol, 1997,
4,
1039-1046.
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PubMed id
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Abstract
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A 108 amino acid protein was designed and constructed from a reduced alphabet of
seven amino acids. The 2.9 A resolution X-ray crystal structure confirms that
the protein is a four helix bundle, as it was designed to be. Hydrogen/deuterium
exchange experiments reveal buried amide protons with protection factors in
excess of 1 x 10(6) in the range characteristic of well protected protons in
functional folded proteins (10(3)-10(8)) rather than protons in rapid exchange
(0-10(2)). The protein is monomeric at 1 mM, the concentration at which the
exchange experiments were undertaken, indicating that the exchange factors are
due to a unique stable tertiary structure fold, and not due to any higher order
quaternary structure. Thermodynamic analysis provides an estimate of the free
energy of folding of -9.3 kcal mole-1 at 25 degrees C, consistent with the free
energy of folding derived from the protection factors of the most protected
protons, indicating that global unfolding is required for exchange of the most
protected protons.
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