Proteins that are site-specifically modified with peptides and chemicals can be used as novel therapeutics, imaging tools, diagnostic reagents and materials. However, there are few enzyme-catalyzed methods currently available to selectively conjugate peptides to internal sites within proteins. Here we show that a pilus-specific sortase enzyme from Corynebacterium diphtheriae (SrtA) can be used to attach a peptide to a protein via a specific lysine-isopeptide bond. Using rational mutagenesis we created SrtA, a highly activated cysteine transpeptidase that catalyzes in vitro isopeptide bond formation. SrtA mediates bioconjugation to a specific lysine residue within a fused domain derived from the corynebacterial SpaA protein. Peptide modification yields greater than >95% can be achieved. We demonstrate that SrtA can be used in concert with the Staphylococcus aureus SrtA enzyme, enabling dual, orthogonal protein labeling via lysine-isopeptide and backbone-peptide bonds.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6230430 | PMC |
http://dx.doi.org/10.1021/jacs.8b05200 | DOI Listing |
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