is it known whether proteincomplexes of which one subunit is polyubiquitinated get degraded, or should each individual protein be ubiquitinated? If not what determinants define that co-degradation occurs?
It should depend on the strength of the given complex. The two complexes that come to my mind (Drystrophin Associated Protein Complex in muscle and P5 complex on endosomes) are both destabilized as soon as one (only the major ?) subunit is missing (in mutants or after RNAi treatment for instance). Then if one subunit of a complex is sent to degradation by ubiquitinylation, I would expect that the complex should be lost as well, but not essentially by ubiquitinylation.
However, we hear for sure more often about these examples because something is happening. They are probably exceptions (and known to be "strong" complexes). We just don't hear about all those complexes that are still stable after the lost of one of their members (compensation...).
I think it is context dependent, it is possible that the degradation of one of the protein in a complex leads to destabilization of whole complex then the other proteins in complex may get destructed.
otherwise the other proteins in complex may stay as subcomplex.
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