Figure 11.

Role of low complexity sequences in promoting the release of a fragment from the proteasome. (A) A protein targeted to the proteasome from the C-terminus will have the C-terminal portion of the protein degraded (green domain), but the presence of a low complexity region and an additional tightly folded domain (blue domain) leads to the release of a fragment consisting of the domain and a tail composed of part or all of the low complexity region. Only the endpoint of degradation is shown. (B) With a normal, high complexity sequence adjacent to the blue domain, a degradation intermediate will form composed of the blue domain bound to the proteasome. This intermediate will then partition between release and degradation, with degradation typically being faster (thicker arrow) leading to overall degradation of the fragment. (C) With a low complexity sequence adjacent to the blue domain, unfolding and degradation is slowed with little or no effect on release, leading to an overall reduction in degradation and accumulation of stable fragment, the same endpoint as shown in plot (A).