The PUL (PLAP, Ufd3p and Lub1p) domain is a novel alpha-helical Ub-associated domain. It directly binds to Cdc48, a chaperone-like AAA ATPase that collects ubiquitylated substrates [2][3].

1: Novel predicted peptidases with a potential role in the ubiquitin signaling pathway. Iyer LM, Koonin EV, Aravind L; Cell Cycle 2004;3:1440-1450. PMID:15483401

2: Doa1 is a Cdc48 adapter that possesses a novel ubiquitin binding domain. Mullally JE, Chernova T, Wilkinson KD; Mol Cell Biol. 2006;26:822-830. PMID:16428438

3: Functional division of substrate processing cofactors of the ubiquitin-selective Cdc48 chaperone. Rumpf S, Jentsch S; Mol Cell. 2006;21:261-269. PMID:16427015