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PDBsum entry 2m0j
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Metal binding protein/metal transport
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PDB id
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2m0j
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References listed in PDB file
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Key reference
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Title
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Binding orientation and specificity of calmodulin to rat olfactory cyclic nucleotide-Gated ion channel.
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Authors
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D.Irene,
J.W.Huang,
T.Y.Chung,
F.Y.Li,
J.T.Tzen,
T.H.Lin,
C.L.Chyan.
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Ref.
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J Biomol Struct Dyn, 2013,
31,
414-425.
[DOI no: ]
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PubMed id
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Note: In the PDB file this reference is
annotated as "TO BE PUBLISHED". The citation details given above have
been manually determined.
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Abstract
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Calmodulin (CaM), the primary intracellular Ca(2+) receptor, regulates a large
number of key enzymes and controls a wide spectrum of important biological
responses. Recognition between CaM and its target sequence in rat olfactory
cyclic nucleotide-gated ion channel (OLFp) was investigated by circular
dichroism (CD), fluorescence, and NMR spectroscopy. Fluorescence data showed the
OLFp tightly bound to CaM with a dissociation constant of 12 nM in a 1:1
stoichiometry. Far-UV CD data showed that approximately 60% of OLFp residues
formed α-helical structures when associated with CaM. NMR data showed that most
of the (15)N-(1)H HSQC cross-peaks of the (15)N-labeled CaM not only shifted but
also split into two sets of peaks upon association with the OLFp. Our data
indicated that the two distinct CaM/OLFp complexes existed simultaneously with
stable structures that were not interexchangeable within the NMR time scale. In
light of the palindromic sequence of OLFp (FQRIVRLVGVIRDW) for CaM targeting, we
proposed that the helical OLFp with C2 symmetry may bind to CaM in two
orientations. This hypothesis is supported by the observation that only one set
of (15)N-(1)H HSQC cross-peaks of the (15)N-labeled CaM was detected upon
association with OLFp-M13 chimeric peptide (OLFMp), a mutated OLFp lacking the
palindromic feature. The binding specificity of OLFMp to CaM was restored when
the palindromic feature was destroyed. Binding modes of CaM/OLFp and CaM/OLFMp
simulated by molecular docking were in accord with their distinct patterns
observed in HSQC spectra. Our studies suggest that the palindromic residues in
OLFp are crucial for the orientation-specific recognition by CaM.
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