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PDBsum entry 3sui
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Calcium-binding protein
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PDB id
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3sui
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References listed in PDB file
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Key reference
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Title
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Distinct properties of ca2+-Calmodulin binding to n- And c-Terminal regulatory regions of the trpv1 channel.
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Authors
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S.Y.Lau,
E.Procko,
R.Gaudet.
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Ref.
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J Gen Physiol, 2012,
140,
541-555.
[DOI no: ]
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PubMed id
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Abstract
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Transient receptor potential (TRP) vanilloid 1 (TRPV1) is a molecular pain
receptor belonging to the TRP superfamily of nonselective cation channels. As a
polymodal receptor, TRPV1 responds to heat and a wide range of chemical stimuli.
The influx of calcium after channel activation serves as a negative feedback
mechanism leading to TRPV1 desensitization. The cellular calcium sensor
calmodulin (CaM) likely participates in the desensitization of TRPV1. Two
CaM-binding sites are identified in TRPV1: the N-terminal ankyrin repeat domain
(ARD) and a short distal C-terminal (CT) segment. Here, we present the crystal
structure of calcium-bound CaM (Ca(2+)-CaM) in complex with the TRPV1-CT
segment, determined to 1.95-Å resolution. The two lobes of Ca(2+)-CaM wrap
around a helical TRPV1-CT segment in an antiparallel orientation, and two
hydrophobic anchors, W787 and L796, contact the C-lobe and N-lobe of Ca(2+)-CaM,
respectively. This structure is similar to canonical Ca(2+)-CaM-peptide
complexes, although TRPV1 contains no classical CaM recognition sequence motif.
Using structural and mutational studies, we established the TRPV1 C terminus as
a high affinity Ca(2+)-CaM-binding site in both the isolated TRPV1 C terminus
and in full-length TRPV1. Although a ternary complex of CaM, TRPV1-ARD, and
TRPV1-CT had previously been postulated, we found no biochemical evidence of
such a complex. In electrophysiology studies, mutation of the Ca(2+)-CaM-binding
site on TRPV1-ARD abolished desensitization in response to repeated application
of capsaicin, whereas mutation of the Ca(2+)-CaM-binding site in TRPV1-CT led to
a more subtle phenotype of slowed and reduced TRPV1 desensitization. In summary,
our results show that the TRPV1-ARD is an important mediator of TRPV1
desensitization, whereas TRPV1-CT has higher affinity for CaM and is likely
involved in separate regulatory mechanisms.
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