Multivalent Site-Specific Phage Modification Enhances
the Binding Affinity of Receptor Ligands
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Abstract
High-throughput screening of combinatorial
chemical libraries is
a powerful approach for identifying targeted molecules. The display
of combinatorial peptide libraries on the surface of bacteriophages
offers a rapid, economical way to screen billions of peptides for
specific binding properties and has impacted fields ranging from cancer
to vaccine development. As a modification to this approach, we have
previously created a system that enables site-specific insertion of
selenocysteine (Sec) residues into peptides displayed pentavalently
on M13 phage as pIII coat protein fusions. In this study, we show
the utility of selectively derivatizing these Sec residues through
the primary amine of small molecules that target a G protein-coupled
receptor, the adenosine A<sub>1</sub> receptor, leaving the other
coat proteins, including the major coat protein pVIII, unmodified.
We further demonstrate that modified Sec-phage with multivalent bound
agonist binds to cells and elicits downstream signaling with orders
of magnitude greater potency than that of unconjugated agonist. Our
results provide proof of concept of a system that can create hybrid
small molecule-containing peptide libraries and open up new possibilities
for phage–drug therapies