endocytosed ldl receptor-associated protein (rap) -coupled ldl receptors dissociate in late endosomes (czekay et al. , 1997) where rap is ubiquitinated and degraded, but ldl receptors are recycled (misra and pizzo , 2001).
When the LDL receptors are first bound to a proteinase inhibitor, it is the LDL receptors that are ubiquitinated.