5wsg
Cryo-EM structure of the Catalytic Step II spliceosome (C* complex) at 4.0 angstrom resolutionCryo-EM structure of the Catalytic Step II spliceosome (C* complex) at 4.0 angstrom resolution
Structural highlights
FunctionMSL1_YEAST Involved in pre-mRNA splicing. This protein is associated with snRNP U2. It binds stem loop IV of U2 snRNA.[1] Publication Abstract from PubMedEach cycle of precursor messenger RNA (pre-mRNA) splicing comprises two sequential reactions, first freeing the 5' exon and generating an intron lariat-3' exon and then ligating the two exons and releasing the intron lariat. The second reaction is executed by the step II catalytically activated spliceosome (known as the C* complex). Here, we present the cryo-electron microscopy structure of a C* complex from Saccharomyces cerevisiae at an average resolution of 4.0 angstroms. Compared with the preceding spliceosomal complex (C complex), the lariat junction has been translocated by 15 to 20 angstroms to vacate space for the incoming 3'-exon sequences. The step I splicing factors Cwc25 and Yju2 have been dissociated from the active site. Two catalytic motifs from Prp8 (the 1585 loop and the beta finger of the ribonuclease H-like domain), along with the step II splicing factors Prp17 and Prp18 and other surrounding proteins, are poised to assist the second transesterification. These structural features, together with those reported for other spliceosomal complexes, yield a near-complete mechanistic picture on the splicing cycle. Structure of a yeast step II catalytically activated spliceosome.,Yan C, Wan R, Bai R, Huang G, Shi Y Science. 2017 Jan 13;355(6321):149-155. doi: 10.1126/science.aak9979. Epub 2016, Dec 15. PMID:27980089[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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