Ubiquitin protein ligase which is a component of the N-end rule pathway with arginine specificity, and functions with the arginyltransferases ATE1 and ATE2. Recognizes and binds to proteins bearing specific N-terminal residues that are destabilizing according to the N-end rule, leading to their ubiquitination and subsequent degradation (PubMed:17572409, PubMed:19255443, PubMed:19620738, PubMed:22020282). Does not participate in degradation of proteins with N-terminal Phe or Leu (PubMed:17572409). The N-end rule pathway regulates seed after-ripening, seedling sugar sensitivity, seedling lipid breakdown, and abscisic acid (ABA) sensitivity of germination (PubMed:19255443). The N-end rule pathway regulates various aspects of leaf and shoot development (PubMed:19620738). Involved in the ubiquitination and subsequent degradation of RAP2-12, an activator of hypoxic gene expression. The ubiquitination occurs after the N-arginylation of RAP2-12 by ATE1 or ATE2 under aerobic conditions (PubMed:22020282). The end-rule pathway plays a role in regulating the timing and amplitude of the immune response following infection with the bacterial pathogen Pseudomonas syringae pv tomato (PubMed:27173012, PubMed:30117535). Regulates the biosynthesis of plant-defense metabolites such as glucosinolates, and the biosynthesis and response to the phytohormone jasmonate (JA), which plays a key role in plant immunity (PubMed:27173012). Controls the expression of specific defense-response genes, activates the synthesis pathway for the phytoalexin camalexin, and influences basal resistance to the hemibiotroph pathogen Pseudomonas syringae pv tomato (PubMed:30117535). Coordinates the mobilization of seed storage reserves and regulates the abundance and activities of several proteases following seed germination (PubMed:29168982). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Reduced seed germination potential and inhibition of seedling establishment by sucrose (PubMed:19255443). Exhibits abnormal shoot and leaf development (PubMed:19620738). Increased tolerance of seedlings to submergence and starvation (PubMed:25667318). Belongs to the UBR1 family. Was originally thought to correspond to two different genes At5g02300 and At5g02310. Was originally thought to correspond to two different genes At5g02300 and At5g02310.