Elucidating <i>Escherichia coli</i> Proteoform Families Using Intact-Mass Proteomics and a Global PTM Discovery Database Yunxiang Dai Michael R. Shortreed Mark Scalf Brian L. Frey Anthony J. Cesnik Stefan Solntsev Leah V. Schaffer Lloyd M. Smith 10.1021/acs.jproteome.7b00516.s001 https://acs.figshare.com/articles/journal_contribution/Elucidating_i_Escherichia_coli_i_Proteoform_Families_Using_Intact-Mass_Proteomics_and_a_Global_PTM_Discovery_Database/5503936 A proteoform family is a group of related molecular forms of a protein (proteoforms) derived from the same gene. We have previously described a strategy to identify proteoforms and elucidate proteoform families in complex mixtures of intact proteins. The strategy is based upon measurements of two properties for each proteoform: (i) the accurate proteoform intact-mass, measured by liquid chromatography/mass spectrometry (LC–MS), and (ii) the number of lysine residues in each proteoform, determined using an isotopic labeling approach. These measured properties are then compared with those extracted from a catalog of theoretical proteoforms containing protein sequences and localized post-translational modifications (PTMs) for the organism under study. A match between the measured properties and those in the catalog constitutes an identification of the proteoform. In the present study, this strategy is extended by utilizing a global PTM discovery database and is applied to the widely studied model organism <i>Escherichia coli</i>, providing the most comprehensive elucidation of <i>E. coli</i> proteoforms and proteoform families to date. 2017-10-02 00:00:00 Elucidating Escherichia coli Proteoform Families model organism Escherichia coli lysine residues proteoform families protein sequences coli proteoforms Intact-Mass Proteomics PTM discovery database LC post-translational modifications proteoform intact-mass proteoform family Global PTM Discovery Database elucidate proteoform families