UC Berkeley

The covalent attachment of chemical groups to proteins is an important tool for many areas of chemical biology, including the study of protein function and the creation of protein-based materials. In order to create well-defined protein bioconjugates, methods of site-specfic protein modification are required. We have developed a high-throughput method of optimizing protein bioconjugation reactions using a combinatorial peptide library in which short peptides serve as a model for protein reactivity. The library screening was achieved using a one-bead-one-compound peptide library, a colorimetric detection scheme to identify high-yielding sequences, and a deconvolution method using a built-in peptide truncation ladder for rapid mass spectrometry sequencing of hit beads. We applied this screening platform in the context of a pyridoxal 5'-phosphate (PLP)-mediated transamination reaction specific for the N-terminus, and were able to identify an N-terminal sequence with high reactivity towards this reaction that can be incorporated into proteins of interest to result in high levels of modification. The screening platform was also used for the discovery and optimization of new N-terminal protein modification reactions.