Fig. 4: The transition from early ED B to mature ED B.
From: Structural insights into human exon-defined spliceosome prior to activation
a Structural changes around the U6/5′SS duplex during the early ED B to mature ED B transition. The PRP8 β-hairpin, together with FBP21 and SF3a120, interacts with the U6/5′SS duplex in the early ED B complex. Recruitment of SNU23, MFAP1, PRP38, and UBL5 leads to formation of the mature ED B complex. b A close-up view on the recognition of the junction region between the exon and 5′SS in the mature ED B complex. Arg9 of UBL5 takes the place of nucleotide C–3 in the late ED pre-B and early ED B states. Trp47 and Tyr48 of UBL5 interact with the Endo-loop and β-hairpin of PRP8, respectively. c A close-up view on the tripartite interface among the exon, MFAP1, and UBL5 in the mature ED B complex. MFAP1 and UBL5 interact with each other through an extensive interface. Both proteins stabilize the 3′-end sequences of the exon.
