title: Allotides: Proline-Rich Cystine Knot α-Amylase Inhibitors from Allamanda cathartica.
abstract: Cystine knot α-amylase inhibitors belong to a knottin family of peptidyl inhibitors of 30-32 residues and contain two to four prolines. Thus far, only four members of the group of cystine knot α-amylase inhibitors have been characterized. Herein, the discovery and characterization of five cystine knot α-amylase inhibitors, allotides C1-C5 (Ac1-Ac5) (1-5), from the medicinal plant Allamanda cathartica are reported using both proteomic and genomic methods. Proteomic analysis showed that 1-5 are 30 amino acids in length with three or four proline residues. NMR determination of 4 revealed that it has two cis- and one trans-proline residues and adopts two equally populated conformations in solution. Determination of disulfide connectivity of 2 by differential S-reduction and S-alkylation provided clues of its unfolding process. Genomic analysis showed that allotide precursors contain a three-domain arrangement commonly found in plant cystine knot peptides with conserved residues flanking the processing sites of the mature allotide domain. This work expands the number of known cystine knot α-amylase inhibitors and furthers the understanding of both the structural and biological diversity of this type of knottin family.
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551.
authors.forename: Phuong Q T
authors.initials: PQ
authors.lastname: Nguyen
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551.
authors.forename: Thuy T
authors.initials: TT
authors.lastname: Luu
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551.
authors.forename: Yang
authors.initials: Y
authors.lastname: Bai
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551.
authors.forename: Giang K T
authors.initials: GK
authors.lastname: Nguyen
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Pervushin
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637551.
authors.forename: James P
authors.initials: JP
authors.lastname: Tam
mesh_terms: D000595:Amino Acid Sequence; D029062:Apocynaceae / Q000737:chemistry*; D003553:Cystine / Q000737:chemistry*; D057771:Cystine-Knot Miniproteins / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D004220:Disulfides / Q000737:chemistry; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010946:Plants, Medicinal / Q000737:chemistry*; D011392:Proline / Q000737:chemistry*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D040901:Proteomics; D012846:Singapore; D000516:alpha-Amylases / Q000037:antagonists & inhibitors*
chemical_list: D057771:Cystine-Knot Miniproteins; D004220:Disulfides; D003553:Cystine; D011392:Proline; D000516:alpha-Amylases