Single-molecule protein sequencing with nanopores

Protein sequencing and the identification of post-translational modifications are key to understanding cellular signalling pathways and metabolic processes in health and disease. Nanopores, that is, nanometre-sized holes in a membrane, were previously put to use for DNA and RNA sequencing, offering single-molecule sensitivity and long read lengths. This prompted efforts to engineer nanopores for the high-throughput sequencing of peptides and proteins. In this Review, we discuss research towards single-molecule protein sequencing using biological nanopores, investigating how their sensitivity allows the discrimination of all 20 amino acids. We outline how fingerprinting of proteins is facilitated by using motor proteins and electro-osmotic flow to promote the slow translocation of proteins through nanopores. Moreover, we examine applications of nanopores to the identification of post-translational modifications, highlighting the potential of this technology for fundamental and clinical proteomic studies. Finally, we outline the advantages and limitations of nanopore systems for protein sequencing and the challenges that remain to be overcome for realizing de novo nanopore protein sequencing.