The eukaryotic N‐end rule pathway mediates ubiquitin‐ and proteasome‐dependent turnover of proteins with a bulky amino‐terminal residue. Arabidopsis locus At5g02310 shows significant similarity to the yeast N‐end rule ligase Ubr1. We demonstrate that At5g02310 is a ubiquitin ligase and mediates degradation of proteins with amino‐terminal Arg residue. Unlike Ubr1, the Arabidopsis protein does not participate in degradation of proteins with amino‐terminal Phe or Leu. This modified target specificity coincides with characteristic differences in domain structure. In contrast to previous publications, our data indicate that At5g02310 is not identical to CER3, a gene involved in establishment of a protective surface wax layer. At5g02310 has therefore been re‐designated PROTEOLYSIS 6 (PRT6), in accordance with its ubiquitin ligase function.