%0 Journal Article %A Burke, Meghan C. %A Wang, Yan %A Lee, Amanda E. %A Dixon, Emma Kimm %A Castaneda, Carlos A. %A Fushman, David %A Fenselau, Catherine %D 2015 %T Unexpected Trypsin Cleavage at Ubiquitinated Lysines %U https://acs.figshare.com/articles/journal_contribution/Unexpected_Trypsin_Cleavage_at_Ubiquitinated_Lysines/2052732 %R 10.1021/acs.analchem.5b01960.s001 %2 https://acs.figshare.com/ndownloader/files/3624084 %K K 48 residues %K trimer %K Lys 48. Trypsin %K R 74 %K ubiquitin %K peptide products %K tryptic conditions %K Ubiquitinated LysinesUnexpected tryptic cleavage %K Initial cleavage %K tryptic products %K Unexpected Trypsin Cleavage %X Unexpected tryptic cleavage has been characterized at modified K48 residues in polyubiquitins. In particular, the tryptic products of all seven of the lysine-linked dimers of ubiquitin and of three trimerslinear Ub–48Ub–48Ub, linear Ub–63Ub–63Ub, and the branched trimer [Ub]26,48Ubhave been analyzed. In addition to the peptide products expected under commonly used tryptic conditions, we observe that peptides are formed with an unexpected ε-glycinylglycinyl-Lys carboxyl terminus when the site of linkage is Lys48. Trypsin from three different commercial sources exhibited this aberration. Initial cleavage at R74 is proposed in a distal ubiquitin to produce a glycinylglycinyl-lysine residue which is bound by trypsin. %I ACS Publications