Discovery and Visualization of Uncharacterized Drug–Protein Adducts Using Mass Spectrometry

Drugs are often metabolized
to reactive intermediates that form
protein adducts. Adducts can inhibit protein activity, elicit immune
responses, and cause life-threatening adverse drug reactions. The
masses of reactive metabolites are frequently unknown, rendering traditional
mass spectrometry-based proteomics approaches incapable of adduct
identification. Here, we present Magnum, an open-mass search algorithm
optimized for adduct identification, and Limelight, a web-based data
processing package for analysis and visualization of data from all
existing algorithms. Limelight incorporates tools for sample comparisons
and xenobiotic-adduct discovery. We validate our tools with three
drug/protein combinations and apply our label-free workflow to identify
novel xenobiotic-protein adducts in CYP3A4. Our new methods and software
enable accurate identification of xenobiotic-protein adducts with
no prior knowledge of adduct masses or protein targets. Magnum outperforms
existing label-free tools in xenobiotic-protein adduct discovery,
while Limelight fulfills a major need in the rapidly developing field
of open-mass searching, which until now lacked comprehensive data
visualization tools.