Two distinct structures of α-conotoxin GI in aqueous solution

Abstract

The detailed analysis of conformational space of α-conotoxin GI in aqueous solution has been performed on the basis of two-dimensional NMR spectroscopy data using multiconformational approach. As the result, two topologically distinct interconvertible sets of GI conformations (populations of 78 % and 22%) have been found. A common feature of the two sets is the Asn4-Cys7 β-turn. The Gly8 to Tyr11 region has a structure of right-handed helical turn in the major set and two sequential bends in the minor one. N- terminus and C-terminus also have different orientations, anti-parallel in the major conformational set and parallel in the minor one. An average pairwise rmsd for backbone heavy atoms is 0.56 Å in the major set, 0.23 Å in the minor, and 1.85 Å between the structures of the two sets. The X-ray structure of GI [Guddat, L. W., Martin, J. A., Shan, L, Edmundson, A. B. and Gray, W. R. (1996) Biochemistry 35, 11 329-11 335] has the same folding pattern as the major NMR set, the average backbone rmsd between the two structures being 0.77 Å.