Distinguishing isomeric N-methylhistidine peptidoforms by ion mobility mass spectrometry

Abstract

Histidine residues in proteins undergo histidine methyltransferase-catalysed Nτ-His and Nπ-His methylation. Here, we demonstrate that ion mobility spectrometry enables separation and identification of peptides possessing the isomeric Nτ-methyl-His and Nπ-methyl-His residues, leading to the assignment of the naturally occurring methyl-His isomer.