Prp8 may insert its β-finger into the first-step complex (U2/U5/U6/pre-mRNA) or U4/U6.U5 tri-snRNP and stabilize these complexes.
Mutations at the base of the β-finger affect U4/U6 unwinding-mediated spliceosome activation. Mutations throughout the β-finger change the conformational equilibrium between the first and the second catalytic step.
The most striking feature of this domain is a β-hairpin finger protruding out of the protein (hence, this domain will be referred to as the β-finger domain), resembling many globular ribosomal proteins with protruding extensions. We present here the crystal structure of a 274-residue domain (residues 1,822–2,095) near the C terminus of Saccharomyces cerevisiae Prp8. Prp8 stands out among hundreds of splicing factors as a key regulator of spliceosome activation and a potential cofactor of the splicing reaction.
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