Fig. 5. Structural homology between TAP and the spliceosomal U2B′′–U2A′ complex. (A) The U2B′′ RNP domain (green) and the U2A′ LRR domain (blue) of the spliceosomal complex with the cognate RNA (in black) (Price et al., 1998). A few residues critical for the macromolecular interactions are highlighted in pink. In orange are two structurally important residues also present in TAP LRR. (B) The RNP domain (green) and LRR domain (in blue) of TAP in one copy in the asymmetric unit of the crystals. In the absence of RNA, the relative orientation of the two domains is likely to be due to crystal packing. Two residues that are structurally important are shown in orange, and some key residues discussed in the text are in pink.