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PDBsum entry 2p3w
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Protein binding
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PDB id
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2p3w
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References listed in PDB file
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Key reference
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Title
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Structural and functional analysis of the pdz domains of human htra1 and htra3.
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Authors
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S.T.Runyon,
Y.Zhang,
B.A.Appleton,
S.L.Sazinsky,
P.Wu,
B.Pan,
C.Wiesmann,
N.J.Skelton,
S.S.Sidhu.
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Ref.
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Protein Sci, 2007,
16,
2454-2471.
[DOI no: ]
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PubMed id
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Abstract
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High-temperature requirement A (HtrA) and its homologs contain a serine protease
domain followed by one or two PDZ domains. Bacterial HtrA proteins and the
mitochondrial protein HtrA2/Omi maintain cell function by acting as both
molecular chaperones and proteases to manage misfolded proteins. The biological
roles of the mammalian family members HtrA1 and HtrA3 are less clear. We report
a detailed structural and functional analysis of the PDZ domains of human HtrA1
and HtrA3 using peptide libraries and affinity assays to define specificity,
structural studies to view the molecular details of ligand recognition, and
alanine scanning mutagenesis to investigate the energetic contributions of
individual residues to ligand binding. In common with HtrA2/Omi, we show that
the PDZ domains of HtrA1 and HtrA3 recognize hydrophobic polypeptides, and while
C-terminal sequences are preferred, internal sequences are also recognized.
However, the details of the interactions differ, as different domains rely on
interactions with different residues within the ligand to achieve high affinity
binding. The results suggest that mammalian HtrA PDZ domains interact with a
broad range of hydrophobic binding partners. This promiscuous specificity
resembles that of bacterial HtrA family members and suggests a similar function
for recognizing misfolded polypeptides with exposed hydrophobic sequences. Our
results support a common activation mechanism for the HtrA family, whereby
hydrophobic peptides bind to the PDZ domain and induce conformational changes
that activate the protease. Such a mechanism is well suited to proteases evolved
for the recognition and degradation of misfolded proteins.
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Figure 3.
Figure 3. Internal peptide ligands for human HtrA PDZ domains. Sequences are shown for peptides selected from an N-terminal
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Figure 6.
Figure 6. Results of shotgun alanine scanning for binding to peptide
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The above figures are
reprinted
by permission from the Protein Society:
Protein Sci
(2007,
16,
2454-2471)
copyright 2007.
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