Antiviral Cystine Knot α-Amylase Inhibitors from Alstonia scholaris

J Biol Chem. 2015 Dec 25;290(52):31138-50. doi: 10.1074/jbc.M115.654855. Epub 2015 Nov 6.

Abstract

Cystine knot α-amylase inhibitors are cysteine-rich, proline-rich peptides found in the Amaranthaceae and Apocynaceae plant species. They are characterized by a pseudocyclic backbone with two to four prolines and three disulfides arranged in a knotted motif. Similar to other knottins, cystine knot α-amylase inhibitors are highly resistant to degradation by heat and protease treatments. Thus far, only the α-amylase inhibition activity has been described for members of this family. Here, we show that cystine knot α-amylase inhibitors named alstotides discovered from the Alstonia scholaris plant of the Apocynaceae family display antiviral activity. The alstotides (As1-As4) were characterized by both proteomic and genomic methods. All four alsotides are novel, heat-stable and enzyme-stable and contain 30 residues. NMR determination of As1 and As4 structures reveals their conserved structural fold and the presence of one or more cis-proline bonds, characteristics shared by other cystine knot α-amylase inhibitors. Genomic analysis showed that they contain a three-domain precursor, an arrangement common to other knottins. We also showed that alstotides are antiviral and cell-permeable to inhibit the early phase of infectious bronchitis virus and Dengue infection, in addition to their ability to inhibit α-amylase. Taken together, our results expand membership of cystine knot α-amylase inhibitors in the Apocynaceae family and their bioactivity, functional promiscuity that could be exploited as leads in developing therapeutics.

Keywords: antiviral agent; cysteine-mediated cross-linking; peptide biosynthesis; peptide conformation; plant biochemistry.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alstonia / chemistry*
  • Alstonia / genetics
  • Animals
  • Antiviral Agents* / chemistry
  • Antiviral Agents* / isolation & purification
  • Antiviral Agents* / pharmacology
  • Chlorocebus aethiops
  • Coronavirus Infections / drug therapy*
  • Coronavirus Infections / metabolism
  • Dengue Virus*
  • Dengue*
  • Glycoside Hydrolase Inhibitors* / chemistry
  • Glycoside Hydrolase Inhibitors* / isolation & purification
  • Glycoside Hydrolase Inhibitors* / pharmacology
  • Infectious bronchitis virus / drug effects*
  • Infectious bronchitis virus / metabolism
  • Plant Proteins* / chemistry
  • Plant Proteins* / genetics
  • Plant Proteins* / isolation & purification
  • Plant Proteins* / pharmacology
  • Protein Structure, Tertiary
  • Vero Cells

Substances

  • Antiviral Agents
  • Glycoside Hydrolase Inhibitors
  • Plant Proteins

Associated data

  • PDB/2mm5
  • PDB/2mm6