1la4 | pdb_00001la4
Solution Structure of SGTx1
Structural highlights
Function[TX1_STRGF] Reversibly inhibits potassium currents in oocytes expressing Kv2.1/KCNB1 channels. Acts by shifting activation of the channel to more depolarized voltages. The toxin may bind to the S3b-S4 helices of the voltage sensor paddle. One, two, three or four toxin molecules may bind the Kv2.1/KCNB1 channel. Partitions into the bilayer membrane, where it stabilizes at the water/membrane interface.[1] [2] Publication Abstract from PubMedSGTx1 is a peptide toxin isolated from the venom of the spider Scodra griseipes that has been shown to inhibit outward K(+) currents in rat cerebellar granule neurons. Although its amino acid sequence is known to be highly (76%) homologous with that of hanatoxin (HaTx), a well-characterized modifier of Kv2.1 channel gating, the structural and functional characteristics of SGTx1 remain largely unknown. Here we describe the NMR solution structure of SGTx1, the mechanism of its interaction with Kv2.1 channels, and its effect on channel activity once bound. The NMR structure of SGTx1 contains a molecular fold closely resembling the "inhibitor cystine knot" of HaTx, which is composed of an antiparallel beta-sheet and four chain reversals stabilized by three disulfide bonds. Functionally, SGTx1 reversibly inhibited K(+) currents in oocytes expressing Kv2.1 channels. Moreover, generation of steady-state activation curves showed that, consistent with other gating modifiers, SGTx1 acted by shifting the activation of the channel to more depolarized voltages. Thus, the surface profile and mechanism of action of SGTx1 are similar to those of HaTx. Still, detailed comparison of SGTx1 with HaTx revealed differences in binding affinity and conformational homogeneity that result from differences in the charge distribution at the binding surface and in the amino acid composition of the respective beta-hairpin structures in the peptides. Solution structure and functional characterization of SGTx1, a modifier of Kv2.1 channel gating.,Lee CW, Kim S, Roh SH, Endoh H, Kodera Y, Maeda T, Kohno T, Wang JM, Swartz KJ, Kim JI Biochemistry. 2004 Feb 3;43(4):890-7. PMID:14744131[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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