Study of molecular and functional diversity of plant cystine knot miniproteins

• Main Author: Nguyen, Quoc Thuc Phuong
• Other Authors: James P. Tam
• Format: Theses and Dissertations
• Language: English
• Published: 2013
• Subjects: DRNTU::Science::Biological sciences::Molecular biology
• Online Access: https://hdl.handle.net/10356/54838
• Institution: Nanyang Technological University

Cystine knot (CK) peptides are structurally diverse and well represented in plant defense system. They are exceptionally stable to thermal denaturation and resistant to proteolytic degradation. As such, they can be used as scaffolds for engineering peptidyl drugs. The focus of my thesis is to isolate and characterize two classes of CK peptides by proteomic and genomic methods. These include α-amylase inhibitors from Apocynaceae and cyclotides from Rubiaceae, Fabaceae, and Poaceae families. From three Apocynaceae species, a family of 30-amino acid-residues α-amylase inhibitors was found, and they are the smallest CK α-amylase inhibitors known to date. In addition, we showed that they are entry inhibitor of a Class I virus by binding to the S and M proteins of infectious bronchitis disease. For cyclotides which are end-to-end cyclic peptides, we studied their biosynthesis and showed that the processing enzymes may be responsible to generate both sequence and form diversity (both linear and cyclic versions). Our work suggests that CK peptides serve as a scaffold to generate molecular diversity in forms, sequences and functions as an evolution advantage for plant defense system.