1N8M

Solution structure of Pi4, a four disulfide bridged scorpion toxin active on potassium channels

Summary for 1N8M

• Entry DOI: 10.2210/pdb1n8m/pdb
• NMR Information: BMRB: 5676
• Descriptor: Potassium channel blocking toxin 4 (1 entity in total)
• Functional Keywords: potassium channel blocker, disulfide bridge stabilized alpha beta motif, toxin
• Cellular location: Secreted: P58498
• Total number of polymer chains: 1
• Total formula weight: 4195.96

Authors

Guijarro, J.I.,M'Barek, S.,Olamendi-Portugal, T.,Gomez-Lagunas, F.,Garnier, D.,Rochat, H.,Possani, L.D.,Sabatier, J.M.,Delepierre, M. (deposition date: 2002-11-21, release date: 2003-09-02, Last modification date: 2024-11-06)

Primary citation

Guijarro, J.I.,M'Barek, S.,Gomez-Lagunas, F.,Garnier, D.,Rochat, H.,Sabatier, J.M.,Possani, L.D.,Delepierre, M.
Solution structure of Pi4, a short four-disulfide-bridged scorpion toxin specific of potassium channels.
Protein Sci., 12:1844-1854, 2003

PubMed Abstract: Pi4 is a short toxin found at very low abundance in the venom of Pandinus imperator scorpions. It is a potent blocker of K(+) channels. Like the other members of the alpha-KTX6 subfamily to which it belongs, it is cross-linked by four disulfide bonds. The synthetic analog (sPi4) and the natural toxin (nPi4) have been obtained by solid-phase synthesis or from scorpion venom, respectively. Analysis of two-dimensional (1)H NMR spectra of nPi4 and sPi4 indicates that both peptides have the same structure. Moreover, electrophysiological recordings of the blocking of Shaker B K(+) channels by sPi4 (K(D) = 8.5 nM) indicate that sPi4 has the same blocking activity of nPi4 (K(D) = 8.0 nM), previously described. The disulfide bonds have been independently determined by NMR and structure calculations, and by Edman-degradation/mass-spectrometry identification of peptides obtained by proteolysis of nPi4. Both approaches indicate that the pairing of the half-cystines is (6)C-(27)C, (12)C-(32)C, (16)C-(34)C, and (22)C-(37)C. The structure of the toxin has been determined by using 705 constraints derived from NMR data on sPi4. The structure, which is well defined, shows the characteristic alpha/beta scaffold of scorpion toxins. It is compared to the structure of the other alpha-KTX6 subfamily members and, in particular, to the structure of maurotoxin, which shows a different pattern of disulfide bridges despite its high degree of sequence identity (76%) with Pi4. The structure of Pi4 and the high amounts of synthetic peptide available, will enable the detailed analysis of the interaction of Pi4 with K(+) channels.

PubMed: 12930984
DOI: 10.1110/ps.03186703

Experimental method

SOLUTION NMR