E3 ubiquitin-protein ligase that limits organ size, and possibly seed size, in a dose-dependent manner. Negatively regulates the duration of cell proliferation in leaves and petals independently of the major phytohormones (e.g. auxin, cytokinin, gibberellin, brassinosteroids, ethylene, abscisic acid, jasmonic acid), probably by targeting growth stimulators for degradation (PubMed:16461280, PubMed:18483219). Limits the proliferation of root meristematic cells (PubMed:28922745). Polyubiquitinates DA1 (PubMed:28167503). Involved in the promotion of leaf senescence, in addition to its function in restricting plant growth (PubMed:28003326). Possesses E3 ubiquitin-protein ligase activity in vitro (PubMed:16461280, PubMed:18483219, PubMed:28167503). 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. Interacts with the E2 ubiquitin conjugating enzyme UBC10 via the RING domain (PubMed:16461280). Interacts with DA1 (PubMed:28167503). Mostly expressed in inflorescence, and, to a lower extent, in seedlings, roots, stems, leaves and siliques. Confined to proliferating cells. Mainly present in proliferating tissues (e.g. root, shoot and floral meristems, and young organs) and vasculature. During petal growth, gradually restricted to the distal part of the petal. Expressed in developing embryos. Rapid turn-over by proteasome-mediated degradation (at protein level). Auto-ubiquitinated. Enlarged floral organs (e.g. petals and sepals) and thick stems mainly due to altered numbers of normally sized cells. Enhanced da1-1 phenotype leading to increased seed and organ size. Plants overexpressing BB exhibit early senescence.