UBA_2 is a domain found on eukaryotic ubiquitin-interacting proteins. Sequestosome 1/p62 has recently been shown to interact with polyubiquitinated proteins through its UBA domain [1]. This domain selectively binds K63-polyubiquitinated proteins.

1: Signaling, polyubiquitination, trafficking, and inclusions: sequestosome 1/p62's role in neurodegenerative disease. Wooten MW, Hu X, Babu JR, Seibenhener ML, Geetha T, Paine MG, Wooten MC; J Biomed Biotechnol. 2006;2006:62079. PMID:17047309