Phage display engineering of peptide substrates in enhancing ligation efficiency of peptide asparaginyl ligase

• Main Author: To, Weng Fui
• Other Authors: James P Tam
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Science::Biological sciences
• Online Access: https://hdl.handle.net/10356/143301
• Institution: Nanyang Technological University

OaAEP1b is a peptide asparaginyl ligase (PAL) that recognizes a C-terminal Asx-containing tripeptide motif (Asn/Asp-X-Y) to generate a site-specific Asn-X peptide bond with an incoming peptide. However, it shows weak peptide cyclase activity, as compared to other PALs, particularly butelase-1, the fastest ligase known to date. Hence, phage display was used in this experiment to select the best binding substrate peptide to enhance the catalytic efficiency of OaAEP1b C247A. In this project, two peptides (Kb-GIYRNGL and b-GIYRNGL) were used as target peptides. A phage library consisting of phage that displayed randomized 7-mer peptides were screened for the best peptide binding sequences to the target peptides in the presence of single mutant OaAEP1b C247A. Four rounds of biopanning led to the discovery of seven peptides (AHSLHWL, AKGHPVM, FPKGKAP, QRFVSNT, RLAWPVH, WSLGYPG, WSLGYTG) that could be potential incoming substrates to the two target peptides in the presence of OaAEP1b C247A.