Guest lecture: Biomimetic Design of Protein Ligands and Applications

Professor Yan Sun, Department of Biochemical Engineering, Tianjin University.

2017.08.18 | Zheng Guo

Date Thu 31 Aug
Time 14:00 16:00
Location Building 3141, room 1.08 (the Seminar room), Gustav wieds vej 10B, 8000 Aarhus

Abstract:
This presentation is concerned with the rational design of protein ligands for protein purification by affinity chromatography and antithrombotic drug design. First of all, aiming at efficient affinity purification of antibodies, we designed affinity peptide ligands of immunoglobulin G (IgG) by mimicking the affinity interactions between Staphylococcal protein A (SpA) and IgG. SpA has been widely used as an affinity ligand for antibody purification. Based on the affinity motif of SpA from protein data bank, we developed a biomimetic design strategy for affinity peptide ligands of IgG, according to the distribution of the six hot spots (amino acid residues) of the SpA affinity motif determined by molecular simulations. The strategy led to the construction of a peptide library containing 2173 heptapeptides and octapeptides. The library was screened by using different molecular simulation protocols, resulting in the selection of 15 affinity peptide candidates. Thereafter, molecular dynamics simulations were performed to validate the dynamics of the affinity interactions between the candidates and IgG, and 14 of them were found to keep high affinities during the simulations. Moreover, all the 15 candidates were coupled to Sepharose gel and evaluated by protein adsorption and chromatographic experiments, As a result, a total of five octapeptides were identified as high-affinity ligands of hIgG. The five ligands were all derived from the same peptide model FYxHxxxE (where x denotes any amino acid) and contained four common hot spots F132, Y133, H137, and E143 of the affinity motif of Protein A. The efficiency of the five affinity ligands was demonstrated by affinity chromatographic purifications of monoclonal antibodies from cell culture media and hIgG from human serum. 

The biomimetic design strategy was extended to the affinity ligand design of the capsomere of virus like particles of murine polyomavirus (MVP) (DWDLRLLY) and collagen (LWWNSYY). DWDLRLLY was experimentally validated by a one-step purification of capsomere from crude cell lysate using affinity chromatography with the octapeptide immobilized on Sepharose gel. The purified capsomeres were observed to self-assemble into VLP with consistent structure of authentic MPV. In the latter case, the binding affinity of LWWNSYY for collagen was demonstrated by isothermal titration calorimetry. Moreover, significant inhibition of platelet adhesion in the presence of LWWNSYY was experimentally validated. Then, an antithrombotic nanoconjugate was designed with LWWNSYY. High efficiency of the nanoconjugate in inhibiting thrombus formation was confirmed in vivo with a murine model by the changes of mean blood flow rate and thrombus weight, indicating its potential for development as a high-efficiency antithrombotic nanomedicine targeting collagen exposed on diseased blood vessel wall.

Biography:
Yan Sun completed his Bachelor of Chemical Engineering in Tianjin University in 1983. He then studied in the University of Tokyo from 1984, and received his Master and Doctor of Engineering Degrees in 1987 and 1990, respectively. After one-year working in a chemical company in Japan, he started his teaching and research career in Tianjin University and became a full Professor in 1993. In 2000, He earned the National Natural Science Foundation of China for Outstanding Young Scientists and was appointed to the Cheung Kong Professorship by the Ministry of Education of China. His areas of expertise include bioseparations, protein refolding, inhibition of amyloid protein aggregation, protein ligand design and discovery, and biocatalysis. His work has produced 360 research papers, a single book (Bioseparations Engineering), two book chapters and 40 patents. He is now an Editor of Journal of Chromatography A, Associate Editor of Biochemical Engineering Journal, and Associate Editor of Chinese Journal of Chemical Engineering.


Coffee and tea will be served.

Lecture / talk