Interaction in vitro; bait produced as a recombinant fusion protein in bacterial system; prey produced as a recombinant fusion protein in bacterial system.

Npl4 binds to ci protein ubiquitinated by the slmb-lin19 (Cul1) E3 conjugating complex (which mediates K11 polyubiquitin linkage), but not the rdx-Cul-3 E3 conjugating complex (which mediates K48 polyubiquitin linkage).

GST-tagged ci bait was phosphorylated and ubiquitinated in vitro using a rabbit system containing E1 and E2 conjugating enzymes, supplemented with either lin19-slmb or Cul-3-rdx E3 conjugating enzymes.