The cwf21 family is involved in mRNA splicing. It has been isolated as a subcomplex of the splicosome in Schizosaccharomyces pombe [1]. The function of the cwf21 domain is to bind directly to the spliceosomal protein Prp8. Mutations in the cwf21 domain prevent Prp8 from binding [2]. The structure of this domain has recently been solved which shows this domain to be composed of two alpha helices.

1: Proteomics analysis reveals stable multiprotein complexes in both fission and budding yeasts containing Myb-related Cdc5p/Cef1p, novel pre-mRNA splicing factors, and snRNAs. Ohi MD, Link AJ, Ren L, Jennings JL, McDonald WH, Gould KL; Mol Cell Biol 2002;22:2011-2024. PMID:11884590

2: Physical and genetic interactions of yeast Cwc21p, an ortholog of human SRm300/SRRM2, suggest a role at the catalytic center of the spliceosome. Grainger RJ, Barrass JD, Jacquier A, Rain JC, Beggs JD; RNA. 2009; [Epub ahead of print] PMID:19854871