RNA recognition motif (RRM) found in vertebrate heterogeneous nuclear ribonucleoprotein C1/C2 (hnRNP C1/C2)
This subgroup corresponds to the RRM of heterogeneous nuclear ribonucleoprotein C (hnRNP) proteins C1 and C2, produced by a single coding sequence. They are the major constituents of the heterogeneous nuclear RNA (hnRNA) ribonucleoprotein (hnRNP) complex in vertebrates. They bind hnRNA tightly, suggesting a central role in the formation of the ubiquitous hnRNP complex. They are involved in the packaging of hnRNA in the nucleus and in processing of pre-mRNA such as splicing and 3'-end formation. hnRNP C proteins contain two distinct domains, an N-terminal RNA recognition motif (RRM), also termed RBD (RNA binding domain) or RNP (ribonucleoprotein domain), and a C-terminal auxiliary domain that includes the variable region, the basic region and the KSG box rich in repeated Lys-Ser-Gly sequences, the leucine zipper, and the acidic region. The RRM is capable of binding poly(U). The KSG box may bind to RNA. The leucine zipper may be involved in dimer formation. The acidic and hydrophilic C-teminus harbors a putative nucleoside triphosphate (NTP)-binding fold and a protein kinase phosphorylation site.