InterPro domain: IPR025704

This is a family of E3 ubiquitin ligase enzymes. Members of this family also include auxin transport protein BIG and protein purity of essence. In humans and mouse, E3 ubiquitin-protein ligase is a component of the N-end rule pathway. It recognises and binds to proteins bearing specific N-terminal residues that are destabilising according to the N-end rule, leading to their ubiquitination and subsequent degradation. Together with clathrin, it forms meshwork structures involved in membrane morphogenesis and cytoskeletal organisation. It also regulates integrin-mediated signaling and may play a role in activation of FAK in response to cell-matrix interactions [ 1 , 2 ].

Auxin transport protein, as suggested by its name, is required for auxin efflux and polar auxin transport (PAT) influencing auxin-mediated developmental responses (e.g. cell elongation, apical dominance, lateral root production, inflorescence architecture, general growth and development) [ 3 ]. Auxin transport protein is also involved in the elongation of the pedicels and stem internodes through auxin action, the expression/modulation of light-regulated genes, repression of CAB1 and CAB3 genes in etiolated seedlings, etc [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ].

Protein purity of essence, found in Drosophila melanogaster, has a role in growth of the perineurial glial layer of the larval peripheral nerve and it may have a role in male fertility and eye development or function [ 12 , 13 , 14 ].

1. p600, a unique protein required for membrane morphogenesis and cell survival. Proc. Natl. Acad. Sci. U.S.A. 102, 15093-8
2. A family of mammalian E3 ubiquitin ligases that contain the UBR box motif and recognize N-degrons. Mol. Cell. Biol. 25, 7120-36
3. BIG: a calossin-like protein required for polar auxin transport in Arabidopsis. Genes Dev. 15, 1985-97
4. Arabidopsis mutants define downstream branches in the phototransduction pathway. Genes Dev. 8, 339-49
5. Reduced naphthylphthalamic acid binding in the tir3 mutant of Arabidopsis is associated with a reduction in polar auxin transport and diverse morphological defects. Plant Cell 9, 745-57
6. Characterization of new gibberellin-responsive semidwarf mutants of arabidopsis. Plant Physiol. 115, 1009-20
7. Mutations in the huge Arabidopsis gene BIG affect a range of hormone and light responses. Plant J. 35, 57-70
8. The auxin transport inhibitor response 3 (tir3) allele of BIG and auxin transport inhibitors affect the gibberellin status of Arabidopsis. Plant J. 41, 231-42
9. An auxin transport independent pathway is involved in phosphate stress-induced root architectural alterations in Arabidopsis. Identification of BIG as a mediator of auxin in pericycle cell activation. Plant Physiol. 137, 681-91
10. CRM1/BIG-mediated auxin action regulates Arabidopsis inflorescence development. Plant Cell Physiol. 48, 1275-90
11. Trichoderma virens, a plant beneficial fungus, enhances biomass production and promotes lateral root growth through an auxin-dependent mechanism in Arabidopsis. Plant Physiol. 149, 1579-92
12. Control of Drosophila perineurial glial growth by interacting neurotransmitter-mediated signaling pathways. Proc. Natl. Acad. Sci. U.S.A. 98, 10445-50
13. Retinal targets for calmodulin include proteins implicated in synaptic transmission. J. Biol. Chem. 273, 31297-307
14. Toward a molecular genetic analysis of spermatogenesis in Drosophila melanogaster: characterization of male-sterile mutants generated by single P element mutagenesis. Genetics 135, 489-505