Covalent attachment of ubiquitin marks substrates for proteolysis, but features that identify ubiquitination targets such as chicken egg white lysozyme are poorly understood. Recognition of lysozyme first requires reduction of Cys-6 Cys-127, one of its four native disulfide bonds, and Cys-6,Cys-127-carboxymethylated (6,127-rcm) lysozyme can mimic this three-disulfide intermediate. The 6,127-rcm...