LysargiNase mirrors trypsin for protein C-terminal and methylation-site identification

To improve proteome coverage and protein C-terminal identification, we characterized the Methanosardna acetivorans thermophilic proteinase LysargiNase, which cleaves before lysine and arginine up to 55 degrees C. Unlike trypsin, LysargiNase-generated peptides had N-terminal lysine or arginine residues and fragmented with b ion dominated spectra. This improved protein C terminal peptide identification and several arginine-rich phosphosite assignments. Notably, cleavage also occurred at methylated or dimethylated lysine and arginine, facilitating detection of these epigenetic modifications.