1H NMR studies of echistatin in solution

Abstract

Two‐dimensional ¹H‐NMR methods have been used to obtain complete proton resonance assignments for the 49‐residue protein echistatin from the viper Echis carinatus. The protein in solution contains only a small amount of regular secondary structure with four very short β‐strands. These β‐strands form two short segments of antiparallel β‐sheet, as evidenced by the observed cross‐strand NOE. The first two strands are connected with a tight reverse turn, whereas the remaining two strands are linked together by an 11‐residue loop forming a so‐called hairpin. The tripeptide unit Arg‐Gly‐Asp, responsible for the binding of echistatin to the fibrinogen receptor glycoprotein GPIIb/IIIa, is located at the tip of this very hydrophilic loop.