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Structural and functional differences of two toxins from the scorpion Pandinus imperator
Author(s) -
Klenk K.C.,
Tenenholz T.C.,
Matteson D.R.,
Rogowski R.S.,
Blaustein M.P.,
Weber D.J.
Publication year - 2000
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/(sici)1097-0134(20000301)38:4<441::aid-prot9>3.0.co;2-l
Subject(s) - biology
The Pandinotoxins, PiTX‐Kα and PiTX‐Kβ, are members of the Charybdotoxin family of scorpion toxins that can be used to characterize K + channels. PiTX‐Kα differs from PiTX‐Kβ, another peptide from Pandinus imperator , by one residue (P10E). When the two toxins are compared in a physiological assay, the affinity of PiTX‐Kβ for voltage‐gated, rapidly inactivating K + channels in dorsal root ganglia (DRG) neurons is 800‐fold lower than that of PiTX‐Kα (Kα‐IC 50 = 8.0 nM versus Kβ‐IC 50 = 6,500 nM). To understand this difference, the three‐dimensional structure of PiTX‐Kβ was determined by nuclear magnetic resonance (NMR) spectroscopy and compared to that of PiTX‐Kα. This comparison shows that structural differences between the two toxins occur at a residue that is critical for blocking K + channels (K27) as well as at the site of the natural mutation (P10E). In PiTX‐Kβ, the negatively charged carboxylate oxygen of E10 can approach the positive charge of K27 and presumably reduces the net positive charge in this region of the toxin. This is likely the reason why PiTX‐Kβ binds K + channels from DRG neurons with a much lower affinity than does PiTX‐Kα. Proteins 2000;38:441–449. © 2000 Wiley‐Liss, Inc.