title: Six alternative proteases for mass spectrometry-based proteomics beyond trypsin.
abstract: Protein digestion using a dedicated protease represents a key element in a typical mass spectrometry (MS)-based shotgun proteomics experiment. Up to now, digestion has been predominantly performed with trypsin, mainly because of its high specificity, widespread availability and ease of use. Lately, it has become apparent that the sole use of trypsin in bottom-up proteomics may impose certain limits in our ability to grasp the full proteome, missing out particular sites of post-translational modifications, protein segments or even subsets of proteins. To overcome this problem, the proteomics community has begun to explore alternative proteases to complement trypsin. However, protocols, as well as expected results generated from these alternative proteases, have not been systematically documented. Therefore, here we provide an optimized protocol for six alternative proteases that have already shown promise in their applicability in proteomics, namely chymotrypsin, LysC, LysN, AspN, GluC and ArgC. This protocol is formulated to promote ease of use and robustness, which enable parallel digestion with each of the six tested proteases. We present data on protease availability and usage including recommendations for reagent preparation. We additionally describe the appropriate MS data analysis methods and the anticipated results in the case of the analysis of a single protein (BSA) and a more complex cellular lysate (Escherichia coli). The digestion protocol presented here is convenient and robust and can be completed in ∼2 d.
authors.affiliation: Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands.|Netherlands Proteomics Centre, Utrecht, the Netherlands.
authors.forename: Piero
authors.initials: P
authors.lastname: Giansanti
authors.affiliation: Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands.|Netherlands Proteomics Centre, Utrecht, the Netherlands.
authors.forename: Liana
authors.initials: L
authors.lastname: Tsiatsiani
authors.affiliation: Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands.|Netherlands Proteomics Centre, Utrecht, the Netherlands.
authors.forename: Teck Yew
authors.initials: TY
authors.lastname: Low
authors.affiliation: Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands.|Netherlands Proteomics Centre, Utrecht, the Netherlands.
authors.forename: Albert J R
authors.identifier: http://orcid.org/0000-0002-2405-4404
authors.initials: AJ
authors.lastname: Heck
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods; D029968:Escherichia coli Proteins / Q000032:analysis / Q000737:chemistry; D007553:Isotope Labeling; D013058:Mass Spectrometry / Q000379:methods*; D010447:Peptide Hydrolases / Q000737:chemistry* / Q000378:metabolism; D010455:Peptides / Q000032:analysis* / Q000737:chemistry; D040901:Proteomics / Q000379:methods*; D011786:Quality Control; D053719:Tandem Mass Spectrometry / Q000379:methods; D014357:Trypsin
chemical_list: D029968:Escherichia coli Proteins; D010455:Peptides; D010447:Peptide Hydrolases; D014357:Trypsin