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Title
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Min-21 and min-23, the smallest peptides that fold like a cystine-stabilized beta-sheet motif: design, solution structure, and thermal stability.
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Authors
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A.Heitz,
D.Le-Nguyen,
L.Chiche.
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Ref.
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Biochemistry, 1999,
38,
10615-10625.
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PubMed id
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Abstract
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Small disulfide-rich proteins provide examples of simple and stable scaffolds
for design purposes. The cystine-stabilized beta-sheet (CSB) motif is one such
elementary structural motif and is found in many protein families with no
evolutionary relationships. In this paper, we present NMR structural studies and
stability measurements of two short peptides of 21 and 23 residues that
correspond to the isolated CSB motif taken from a 28-residue squash trypsin
inhibitor. The two peptides contain two disulfide bridges instead of three for
the parent protein, but were shown to fold in a native-like fashion, indicating
that the CSB motif can be considered an autonomous folding unit. The 23-residue
peptide was truncated at the N-terminus. It has a well-defined conformation
close to that of the parent squash inhibitor, and although less stable than the
native protein, it still exhibits a high T(m) of about 100 degrees C. We suggest
that this peptide is a very good starting building block for engineering new
bioactive molecules by grafting different active or recognition sites onto it.
The 21-residue peptide was further shortened by removing two residues in the
loop connecting the second and third cysteines. This peptide exhibited a less
well-defined conformation and is less stable by about 1 kcal mol(-)(1), but it
might be useful if a higher flexibility is desired. The lower stability of the
21-residue peptide is supposed to result from inadequate lengths of segments
connecting the first three cysteines, thus providing new insights into the
structural determinants of the CSB motif.
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