Figure 9.
New roles for Ser65-phosphoUb
Phosphorylation of Ub by PINK1 has multiple consequences. Structurally, it alters the electrostatic potential of Ub, but also generates a new UbretraCT conformation with a retracted C-terminus. The UbretraCT conformation is in slow exchange with the common Ub conformation. Functionally, Ub phosphorylation leads to a gain-of-function of Ub, as it becomes an allosteric activator of Parkin. We here show that phosphoUb also has loss-of-function effects, as it inhibits some assembly and disassembly systems. Additionally, it is possible that phosphoUb is recognized specifically by Ub receptors.