RNA recognition motif (RRM) found in U11/U12 small nuclear ribonucleoprotein 35 kDa protein (U11/U12-35K) and similar proteins
This subfamily corresponds to the RRM of U11/U12-35K, also termed protein HM-1, or U1 snRNP-binding protein homolog, and is one of the components of the U11/U12 snRNP, which is a subunit of the minor (U12-dependent) spliceosome required for splicing U12-type nuclear pre-mRNA introns. U11/U12-35K is highly conserved among bilateria and plants, but lacks in some organisms, such as Saccharomyces cerevisiae and Caenorhabditis elegans. Moreover, U11/U12-35K shows significant sequence homology to U1 snRNP-specific 70 kDa protein (U1-70K or snRNP70). It contains a conserved RNA recognition motif (RRM), also termed RBD (RNA binding domain) or RNP (ribonucleoprotein domain), followed by an adjacent glycine-rich region, and Arg-Asp and Arg-Glu dipeptide repeats rich domain, making U11/U12-35K a possible functional analog of U1-70K. It may facilitate 5' splice site recognition in the minor spliceosome and play a role in exon bridging, interacting with components of the major spliceosome bound to the pyrimidine tract of an upstream U2-type intron. The family corresponds to the RRM of U11/U12-35K that may directly contact the U11 or U12 snRNA through the RRM domain.