Extended Data Figure 3: Protein–RNA interactions in the catalytic RNP core of the C* complex.
From: Cryo-EM structure of a human spliceosome activated for step 2 of splicing
a, Domain structure of the human PRP8 protein. b, c, The catalytic U2–U6 RNA core is shown docked into the active-site pocket of PRP8 (space filling model) in the human C* and S. cerevisiae C complex22. BS, branch site. d, Interaction of the N-terminal HAT repeats of SYF3 and the linker between PRP8 NTD1 and 2 with the U6 ISL in the C* complex. e, Interaction of the CDC5 Myb domain with U2/U6 helix Ia. f, Interaction of WD40 domain of PRL1 with U5 stem Ic and the loop of the U6 ISL. Not only is the docking of the U2–U6 RNA core within the active site pocket of PRP8 similar in C and C*, but also the interaction of the linker between PRP8 NTD1 and 2 with the major groove of the U6 ISL, of SYF3 with the lower stem of the U6 ISL, and of the CDC5 Myb domain with the U2/U6 helix Ia. Moreover, the WD40 domain of PRL1 interacts with U5 stem Ic and the U6 ISL loop in both organisms14,21,22 and α-helix 2 of CDC5 runs along the groove of the U6 ACAGA box helix (Extended Data Fig. 5b). N-terminal parts of Skip and Ad002 (amino acid positions are indicated) also contact the U6 ISL.
