Solution structure of the major α-amylase inhibitor of the crop plant amaranth

Shanyun Lu, Pengchi Deng, Xiucai Liu, Jingchu Luo, Rushan Han, Xiaocheng Gu, Songping Liangi, Xianchun Wang, Feng Li, Valentin Lozanov, András Patthy, Sándor Pongor

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α-Amylase inhibitor (AAI), a 32-residue miniprotein from the Mexican crop plant amaranth (Amaranthus hypochondriacus), is the smallest known α- amylase inhibitor and is specific for insect α-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 Å for the backbone atoms and 1.04 Å for all heavy atoms. The structure of AAI consists of a short triple-stranded β- 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.

Original languageEnglish
Pages (from-to)20473-20478
Number of pages6
JournalJournal of Biological Chemistry
Issue number29
Publication statusPublished - Jul 16 1999

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    Lu, S., Deng, P., Liu, X., Luo, J., Han, R., Gu, X., Liangi, S., Wang, X., Li, F., Lozanov, V., Patthy, A., & Pongor, S. (1999). Solution structure of the major α-amylase inhibitor of the crop plant amaranth. Journal of Biological Chemistry, 274(29), 20473-20478.