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Structural insights into the mechanism of activation of the TRPV1 channel by a membrane-bound tarantula toxin.

Bae C, Anselmi C, Kalia J, Jara-Oseguera A, Schwieters CD, Krepkiy D, Won Lee C, Kim EH, Kim JI, Faraldo-Gómez JD, Swartz KJ - Elife (2016)

Bottom Line: We also provide improved structures of TRPV1 with and without the toxin bound, and investigate the interactions of DkTx with the channel and membranes.Finally, we find that the toxin disrupts a cluster of hydrophobic residues behind the selectivity filter that are critical for channel activation.Collectively, our findings reveal a novel mode of toxin-channel recognition that has important implications for the mechanism of thermosensation.

View Article: PubMed Central - PubMed

Affiliation: Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States.

ABSTRACT
Venom toxins are invaluable tools for exploring the structure and mechanisms of ion channels. Here, we solve the structure of double-knot toxin (DkTx), a tarantula toxin that activates the heat-activated TRPV1 channel. We also provide improved structures of TRPV1 with and without the toxin bound, and investigate the interactions of DkTx with the channel and membranes. We find that DkTx binds to the outer edge of the external pore of TRPV1 in a counterclockwise configuration, using a limited protein-protein interface and inserting hydrophobic residues into the bilayer. We also show that DkTx partitions naturally into membranes, with the two lobes exhibiting opposing energetics for membrane partitioning and channel activation. Finally, we find that the toxin disrupts a cluster of hydrophobic residues behind the selectivity filter that are critical for channel activation. Collectively, our findings reveal a novel mode of toxin-channel recognition that has important implications for the mechanism of thermosensation.

No MeSH data available.


Summary of 3JHNHα coupling constant and proton chemical shifts of DkTx in solution.(A) Summary of 3JHNHα coupling constants, secondary structure elements, and chemical shift index (CSI) for DkTx. Values of 3JHNHα are represented as ↑ (>8 Hz) or ↓(<5.5Hz). (B) Chemical shift comparison between K1/K2 lobes and DkTx. Chemical shift difference (ΔCS in ppm) between K1/K2 lobe and DkTx was calculated according to ΔCS = [(ΔδHα)2+(ΔδHN)2]1/2, where ΔδHα denotes Hα chemical shift difference between DkTx and K1/K2, and ΔδHN denotes HN chemical shift difference between DkTx and K1/K2.DOI:http://dx.doi.org/10.7554/eLife.11273.006
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fig1s3: Summary of 3JHNHα coupling constant and proton chemical shifts of DkTx in solution.(A) Summary of 3JHNHα coupling constants, secondary structure elements, and chemical shift index (CSI) for DkTx. Values of 3JHNHα are represented as ↑ (>8 Hz) or ↓(<5.5Hz). (B) Chemical shift comparison between K1/K2 lobes and DkTx. Chemical shift difference (ΔCS in ppm) between K1/K2 lobe and DkTx was calculated according to ΔCS = [(ΔδHα)2+(ΔδHN)2]1/2, where ΔδHα denotes Hα chemical shift difference between DkTx and K1/K2, and ΔδHN denotes HN chemical shift difference between DkTx and K1/K2.DOI:http://dx.doi.org/10.7554/eLife.11273.006

Mentions: Complete proton resonance assignments for K1 and K2 were made using traditional 2D NMR sequential assignment techniques (Wüthrich, 1986) (Figure 1—figure supplement 1). Using the proton chemical shift values of isolated K1 and K2 as reference, proton resonances in DkTx were readily identified (Figure 1—figure supplement 1,2). The backbone proton chemical shift values of DkTx were found to be nearly identical to those measured for K1 and K2 separately, except for a few residues in the linker region and in the N- and C-termini of the toxin (Figure 1—figure supplement 3). We can therefore conclude that the structures of isolated K1 and K2 are highly similar to those in full-length DkTx.


Structural insights into the mechanism of activation of the TRPV1 channel by a membrane-bound tarantula toxin.

Bae C, Anselmi C, Kalia J, Jara-Oseguera A, Schwieters CD, Krepkiy D, Won Lee C, Kim EH, Kim JI, Faraldo-Gómez JD, Swartz KJ - Elife (2016)

Summary of 3JHNHα coupling constant and proton chemical shifts of DkTx in solution.(A) Summary of 3JHNHα coupling constants, secondary structure elements, and chemical shift index (CSI) for DkTx. Values of 3JHNHα are represented as ↑ (>8 Hz) or ↓(<5.5Hz). (B) Chemical shift comparison between K1/K2 lobes and DkTx. Chemical shift difference (ΔCS in ppm) between K1/K2 lobe and DkTx was calculated according to ΔCS = [(ΔδHα)2+(ΔδHN)2]1/2, where ΔδHα denotes Hα chemical shift difference between DkTx and K1/K2, and ΔδHN denotes HN chemical shift difference between DkTx and K1/K2.DOI:http://dx.doi.org/10.7554/eLife.11273.006
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Related In: Results  -  Collection

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fig1s3: Summary of 3JHNHα coupling constant and proton chemical shifts of DkTx in solution.(A) Summary of 3JHNHα coupling constants, secondary structure elements, and chemical shift index (CSI) for DkTx. Values of 3JHNHα are represented as ↑ (>8 Hz) or ↓(<5.5Hz). (B) Chemical shift comparison between K1/K2 lobes and DkTx. Chemical shift difference (ΔCS in ppm) between K1/K2 lobe and DkTx was calculated according to ΔCS = [(ΔδHα)2+(ΔδHN)2]1/2, where ΔδHα denotes Hα chemical shift difference between DkTx and K1/K2, and ΔδHN denotes HN chemical shift difference between DkTx and K1/K2.DOI:http://dx.doi.org/10.7554/eLife.11273.006
Mentions: Complete proton resonance assignments for K1 and K2 were made using traditional 2D NMR sequential assignment techniques (Wüthrich, 1986) (Figure 1—figure supplement 1). Using the proton chemical shift values of isolated K1 and K2 as reference, proton resonances in DkTx were readily identified (Figure 1—figure supplement 1,2). The backbone proton chemical shift values of DkTx were found to be nearly identical to those measured for K1 and K2 separately, except for a few residues in the linker region and in the N- and C-termini of the toxin (Figure 1—figure supplement 3). We can therefore conclude that the structures of isolated K1 and K2 are highly similar to those in full-length DkTx.

Bottom Line: We also provide improved structures of TRPV1 with and without the toxin bound, and investigate the interactions of DkTx with the channel and membranes.Finally, we find that the toxin disrupts a cluster of hydrophobic residues behind the selectivity filter that are critical for channel activation.Collectively, our findings reveal a novel mode of toxin-channel recognition that has important implications for the mechanism of thermosensation.

View Article: PubMed Central - PubMed

Affiliation: Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States.

ABSTRACT
Venom toxins are invaluable tools for exploring the structure and mechanisms of ion channels. Here, we solve the structure of double-knot toxin (DkTx), a tarantula toxin that activates the heat-activated TRPV1 channel. We also provide improved structures of TRPV1 with and without the toxin bound, and investigate the interactions of DkTx with the channel and membranes. We find that DkTx binds to the outer edge of the external pore of TRPV1 in a counterclockwise configuration, using a limited protein-protein interface and inserting hydrophobic residues into the bilayer. We also show that DkTx partitions naturally into membranes, with the two lobes exhibiting opposing energetics for membrane partitioning and channel activation. Finally, we find that the toxin disrupts a cluster of hydrophobic residues behind the selectivity filter that are critical for channel activation. Collectively, our findings reveal a novel mode of toxin-channel recognition that has important implications for the mechanism of thermosensation.

No MeSH data available.