On Sequencing a Protein with Nanopores, tRNAs, and RNAs with Terminal Codons

A method for indirectly sequencing a protein from a codon sequence is proposed. An unfolded protein molecule is threaded through a nano-sized pore in an electrolytic cell carboxyl end first and held with a voltage such that only the first residue is exposed in the trans chamber of the cell. A tRNA molecule in trans with matching anticodon for the residue binds itself to the latter in the presence of suitable catalysts. It is then cleaved and transferred to an extended electrolytic cell with N pores, 40 ≤ N ≤ 61, in N individual cis chambers and a single trans chamber. Each of the N pores holds an RNA molecule ending in a unique codon that is held exposed in the trans chamber. In the presence of suitable catalysts the anticodon in the transferred tRNA binds with the codon of a matching RNA molecule. By reversing the voltages in the extended electrolytic cell every RNA molecule except the one to which the transferred tRNA is bound recedes into its cis chamber, this identifies the residue unambiguously. The detected residue in the first cell is cleaved and the process repeated. A feasibility analysis is presented for the proposed scheme. The method is suitable for de novo sequencing as no a priori information about the protein is needed.