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. Author manuscript; available in PMC: 2013 May 23.
Published in final edited form as: Nat Rev Microbiol. 2009 Jun 1;7(7):485–491. doi: 10.1038/nrmicro2148

Fig. 2. Proposed model of the Pup-proteasome pathway in Mtb.

Fig. 2

Unlike Ub, Pup is not processed proteolytically from a larger precursor protein. Pup appears to be de-amidated at the C-terminal Gln. From this point, it has been proposed that PafA phosphorylates the γ-carboxylate of the C-terminus of Pup, but this has not been established. The attachment of Pup to the substrate Lys can potentially be via either the α- or γ-carboxylate. It is not known if poly-pupylation occurs, nor is it known if Pup is removed by a de-pupylase (“DPUP”) prior to degradation, and recycled like Ub.