The Human Cdc34 Carboxyl Terminus Contains a Non-covalent Ubiquitin Binding Activity That

Cdc34isanE2ubiquitin-conjugatingenzymethatfunctionsinconjunctionwithSCF(Skp1Cullin1F-box)E3ubiquitinligasetocat-alyzecovalentattachmentofpolyubiquitinchainstoatargetprotein.Here we identified direct interactions between the human Cdc34 Cterminus and ubiquitin using NMR chemical shift perturbationassays. The ubiquitin binding activity was mapped to two separateCdc34 C-terminal motifs (UBS1 and UBS2) that comprise residues206–215 and 216–225, respectively. UBS1 and UBS2 bind to ubiq-uitin in the proximity of ubiquitin Lys