Single-molecule site-specific detection of protein phosphorylation with a nanopore.

We demonstrate single-molecule, site-specific detection of protein phosphorylation with protein nanopore technology. A model protein, thioredoxin, was phosphorylated at two adjacent sites. Analysis of the ionic current amplitude and noise, as the protein unfolds and moves through an α-hemolysin pore, enables the distinction between unphosphorylated, monophosphorylated and diphosphorylated variants. Our results provide a step toward nanopore proteomics.