1qfd

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Template:STRUCTURE 1qfd

NMR SOLUTION STRUCTURE OF ALPHA-AMYLASE INHIBITOR (AAI)

Overview

alpha-Amylase inhibitor (AAI), a 32-residue miniprotein from the Mexican crop plant amaranth (Amaranthus hypochondriacus), is the smallest known alpha-amylase inhibitor and is specific for insect alpha-amylases (Chagolla-Lopez, A., Blanco-Labra, A., Patthy, A., Sanchez, R., and Pongor, S. (1994) J. Biol. Chem. 269, 23675-23680). Its disulfide topology was confirmed by Edman degradation, and its three-dimensional solution structure was determined by two-dimensional 1H NMR spectroscopy at 500 MHz. Structural constraints (consisting of 348 nuclear Overhauser effect interproton distances, 8 backbone dihedral constraints, and 9 disulfide distance constraints) were used as an input to the X-PLOR program for simulated annealing and energy minimization calculations. The final set of 10 structures had a mean pairwise root mean square deviation of 0.32 A for the backbone atoms and 1.04 A for all heavy atoms. The structure of AAI consists of a short triple-stranded beta-sheet stabilized by three disulfide bonds, forming a typical knottin or inhibitor cystine knot fold found in miniproteins, which binds various macromolecular ligands. When the first intercystine segment of AAI (sequence IPKWNR) was inserted into a homologous position of the spider toxin Huwentoxin I, the resulting chimera showed a significant inhibitory activity, suggesting that this segment takes part in enzyme binding.

About this Structure

1QFD is a Single protein structure of sequence from Amaranthus hypochondriacus. Full crystallographic information is available from OCA.

Reference

Solution structure of the major alpha-amylase inhibitor of the crop plant amaranth., Lu S, Deng P, Liu X, Luo J, Han R, Gu X, Liang S, Wang X, Li F, Lozanov V, Patthy A, Pongor S, J Biol Chem. 1999 Jul 16;274(29):20473-8. PMID:10400675 Page seeded by OCA on Sat May 3 06:12:05 2008