Cis-trans recognition and subunit-specific degradation of short-lived proteins

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Abstract
THE N-end rule, a code that relates the metabolic stability of a protein to the identity of its ammo-terminal residue1, is universal in that different versions of the N-end rule operate in mammals2–5, yeast1,6,7 and bacteria (unpublished data). The N-end rule-based degradation signal comprises a destabilizing amino-terminal residue and a specific internal lysine residue1,6,7. We now show that, in a multisubunit protein, these two determinants can be located on different subunits and still target the protein for destruction. Moreover, in this case (trans recognition) only the subunit that bears the lysine determinant is actually degraded. Thus an oligomeric protein can contain both short-lived and long-lived subunits. These insights have functional and practical implications.