Format

Send to

Choose Destination
J Biol Chem. 2007 Apr 27;282(17):12687-97. Epub 2007 Mar 5.

Molecular interactions of the gating modifier toxin ProTx-II with NaV 1.5: implied existence of a novel toxin binding site coupled to activation.

Author information

1
Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York, Buffalo, New York 14214, USA.

Abstract

Voltage-gated Na(+) channels are critical components in the generation of action potentials in excitable cells, but despite numerous structure-function studies on these proteins, their gating mechanism remains unclear. Peptide toxins often modify channel gating, thereby providing a great deal of information about these channels. ProTx-II is a 30-amino acid peptide toxin from the venom of the tarantula, Thrixopelma pruriens, that conforms to the inhibitory cystine knot motif and which modifies activation kinetics of Na(v) and Ca(v), but not K(v), channels. ProTx-II inhibits current by shifting the voltage dependence of activation to more depolarized potentials and, therefore, differs from the classic site 4 toxins that shift voltage dependence of activation in the opposite direction. Despite this difference in functional effects, ProTx-II has been proposed to bind to neurotoxin site 4 because it modifies activation. Here, we investigate the bioactive surface of ProTx-II by alanine-scanning the toxin and analyzing the interactions of each mutant with the cardiac isoform, Na(v)1.5. The active face of the toxin is largely composed of hydrophobic and cationic residues, joining a growing group of predominantly K(v) channel gating modifier toxins that are thought to interact with the lipid environment. In addition, we performed extensive mutagenesis of Na(v)1.5 to locate the receptor site with which ProTx-II interacts. Our data establish that, contrary to prior assumptions, ProTx-II does not bind to the previously characterized neurotoxin site 4, thus making it a novel probe of activation gating in Na(v) channels with potential to shed new light on this process.

PMID:
17339321
DOI:
10.1074/jbc.M610462200
[Indexed for MEDLINE]
Free full text

Supplemental Content

Full text links

Icon for HighWire
Loading ...
Support Center