Peptide-displaying phage technology in glycobiology

Abstract

Phage display technology is an emerging drug discovery tool. Using that approach, short peptides that mimic part of a carbohydrate's conformation are selected by screening a peptide-displaying phage library with anti-carbohydrate antibodies. Chemically synthesized peptides with an identified sequence have been used as an alternative ligand to carbohydrate-binding proteins. These peptides represent research tools useful to assay the activities of glycosyltransferases and/or sulfotransferases or to inhibit the carbohydrate-dependent binding of proteins in vitro and in vivo. Peptides can also serve as immunogens to raise anti-carbohydrate antibodies in vivo in animals. Phage display has also been used in single-chain antibody technology by inserting an immunoglobulin's variable region sequence into the phage. A single-chain antibody library can then be screened with a carbohydrate antigen as the target, resulting in a recombinant anti-carbohydrate antibody with high affinity to the antigen. This review provides examples of successful applications of peptide-displaying phage technology to glycobiology. Such an approach should benefit translational research by supplying carbohydrate-mimetic peptides and carbohydrate-binding polypeptides.

Fig. 1.

Biopanning of T7-based peptide-displaying phage library. A phage library consisting of as many as 10^9–10 clones is added to a plastic well coated with a target, such as a monoclonal anti-carbohydrate antibody. Phage clones that do not bind the target will be washed away from the plate. Competent host bacteria are then added to the well, so that phages remaining in the well will infect bacteria. Following the growth of infected bacteria, the phages are amplified. By repeating this procedure 3–4 rounds, phage clones displaying peptides with high target-binding affinity are isolated. Biopanning of the filamentous M13-based phage can be done in a similar manner.

Fig. 2.

Schematic illustration of the IgG antibody, Fab fragment of IgG and single-chain (scFv) antibody.