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PDBsum entry 2kdl
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Human serum albumin binding protein
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PDB id
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2kdl
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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 minimal sequence code for switching protein structure and function.
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Authors
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P.A.Alexander,
Y.He,
Y.Chen,
J.Orban,
P.N.Bryan.
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Ref.
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Proc Natl Acad Sci U S A, 2009,
106,
21149-21154.
[DOI no: ]
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PubMed id
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Abstract
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We present here a structural and mechanistic description of how a protein
changes its fold and function, mutation by mutation. Our approach was to create
2 proteins that (i) are stably folded into 2 different folds, (ii) have 2
different functions, and (iii) are very similar in sequence. In this simplified
sequence space we explore the mutational path from one fold to another. We show
that an IgG-binding, 4beta+alpha fold can be transformed into an
albumin-binding, 3-alpha fold via a mutational pathway in which neither function
nor native structure is completely lost. The stabilities of all mutants along
the pathway are evaluated, key high-resolution structures are determined by NMR,
and an explanation of the switching mechanism is provided. We show that the
conformational switch from 4beta+alpha to 3-alpha structure can occur via a
single amino acid substitution. On one side of the switch point, the 4beta+alpha
fold is >90% populated (pH 7.2, 20 degrees C). A single mutation switches the
conformation to the 3-alpha fold, which is >90% populated (pH 7.2, 20 degrees
C). We further show that a bifunctional protein exists at the switch point with
affinity for both IgG and albumin.
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Figure 4.
Cartoon depiction of backbone topology of G[A]95 and G[B]95.
Residues 1–8 are blue, 9–23 are green, 24–37 are red,
38–52 are yellow, and 53–56 are cyan.
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Figure 6.
Switching mechanism. Alternative conformations of the
N-terminal (orange) and C-terminal (blue) amino acids in the
3-α and 4β+α folds. The critical switch amino acid occurs at
position 45 (red). Also depicted are the hydrophobic packing of
the N- and C-terminal amino acids in the core of the 4β+α fold.
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