Structural and functional domains of human TAP bound to p15. The cargo-binding domain of TAP (residues 1 to 372) consists of an RNP-type RNA-binding domain (RBD, residues 119 to 198), a leucine-rich repeat domain (LRR, residues 203 to 362), and a less well conserved region N-terminal to the RBD for which no structural information is available (residues 1 to 119). The NPC-binding domain of TAP consists of the NTF2-like domain (grey square, residues 371 to 551) bound to p15 (black square) and a UBA-like domain (triangle, residues 563 to 619). Each of these domains features a nucleoporin-binding site (solid diamond).