RNA recognition motif (RRM) superfamily; RRM, also known as RBD (RNA binding domain) or RNP (ribonucleoprotein domain), is a highly abundant domain in eukaryotes found in proteins involved in post-transcriptional gene expression processes including mRNA and rRNA processing, RNA export, and RNA stability. This domain is 90 amino acids in length and consists of a four-stranded beta-sheet packed against two alpha-helices. RRM usually interacts with ssRNA, but is also known to interact with ssDNA as well as proteins. RRM binds a variable number of nucleotides, ranging from two to eight. The active site includes three aromatic side-chains located within the conserved RNP1 and RNP2 motifs of the domain. The RRM domain is found in a variety heterogeneous nuclear ribonucleoproteins (hnRNPs), proteins implicated in regulation of alternative splicing, and protein components of small nuclear ribonucleoproteins (snRNPs).

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gi 1033937341  85 D*PPNQILFLTNLPEET*E 103
Cdd:cd12479     1 EQPPNQILFLTNLPEETNE 19

RNA recognition motif 2 (RRM2) found in Drosophila melanogaster sex determination protein SNF and similar proteins; This subgroup corresponds to the RRM2 of SNF (Sans fille), also termed U1 small nuclear ribonucleoprotein A (U1 snRNP A or U1-A or U1A), an RNA-binding protein found in the U1 and U2 snRNPs of Drosophila. It is essential in Drosophila sex determination and possesses a novel dual RNA binding specificity. SNF binds with high affinity to both Drosophila U1 snRNA stem-loop II (SLII) and U2 snRNA stem-loop IV (SLIV). It can also bind to poly(U) RNA tracts flanking the alternatively spliced Sex-lethal (Sxl) exon, as does Drosophila Sex-lethal protein (SXL). SNF contains two RNA recognition motifs (RRMs); it can self-associate through RRM1, and each RRM can recognize poly(U) RNA binding independently.

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gi 1033937341  85 D*PPNQILFLTNLPEET*E 103
Cdd:cd12479     1 EQPPNQILFLTNLPEETNE 19

RNA recognition motif 1 (RRM1) found in vertebrate U1 small nuclear ribonucleoprotein A (U1A); This subgroup corresponds to the RRM1 of U1A (also termed U1 snRNP A or U1-A), an RNA-binding protein associated with the U1 snRNP, a small RNA-protein complex involved in pre-mRNA splicing. U1A binds with high affinity and specificity to stem-loop II (SLII) of U1 snRNA. It is predominantly a nuclear protein and it also shuttles between the nucleus and the cytoplasm independently of interactions with U1 snRNA. U1A may be involved in RNA 3'-end processing, specifically cleavage, splicing and polyadenylation, through interacting with a large number of non-snRNP proteins, including polypyrimidine tract binding protein (PTB), polypyrimidine-tract binding protein-associated factor (PSF), and non-POU-domain-containing, octamer-binding (NONO), DEAD (Asp-Glu-Ala-Asp) box polypeptide 5 (DDX5). It also binds to a flavivirus NS5 protein and plays an important role in virus replication. U1A contains two RNA recognition motifs (RRMs); the N-terminal RRM (RRM1) binds tightly and specifically to the U1 snRNA SLII and its own 3'-UTR, while in contrast, the C-terminal RRM (RRM2) does not appear to associate with any RNA and may be free to bind other proteins. U1A also contains a proline-rich region, and a nuclear localization signal (NLS) in the central domain that is responsible for its nuclear import.

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gi 1033937341   1 ALVVFREISSASNALRTMQGFPFYDKPMRIAYAKTDSDIVA 41
Cdd:cd12477    49 AFVIFKEVSSATNALRSMQGFPFYDKPMRIQYAKTDSDIIA 89

RNA recognition motif 1 (RRM1) found in Drosophila melanogaster sex determination protein SNF and similar proteins; This subgroup corresponds to the RRM1 of SNF (Sans fille), also termed U1 small nuclear ribonucleoprotein A (U1 snRNP A or U1-A or U1A), an RNA-binding protein found in the U1 and U2 snRNPs of Drosophila. It is essential in Drosophila sex determination and possesses a novel dual RNA binding specificity. SNF binds with high affinity to both Drosophila U1 snRNA stem-loop II (SLII) and U2 snRNA stem-loop IV (SLIV). It can also bind to poly(U) RNA tracts flanking the alternatively spliced Sex-lethal (Sxl) exon, as does Drosophila Sex-lethal protein (SXL). SNF contains two RNA recognition motifs (RRMs); it can self-associate through RRM1, and each RRM can recognize poly(U) RNA binding independently.

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gi 1033937341   1 ALVVFREISSASNALRTMQGFPFYDKPMRIAYAK 34
Cdd:cd12476    52 AFVIFKDISSATNALRSMQGFPFYDKPMRIAYSK 85

RNA recognition motif 2 (RRM2) found in vertebrate U1 small nuclear ribonucleoprotein A (U1 snRNP A or U1-A or U1A); This subgroup corresponds to the RRM2 of U1A (also termed U1 snRNP A or U1-A), an RNA-binding protein associated with the U1 snRNP, a small RNA-protein complex involved in pre-mRNA splicing. U1A binds with high affinity and specificity to stem-loop II (SLII) of U1 snRNA. It is predominantly a nuclear protein that shuttles between the nucleus and the cytoplasm independently of interactions with U1 snRNA. U1A may be involved in RNA 3'-end processing, specifically cleavage, splicing and polyadenylation, through interacting with a large number of non-snRNP proteins, including polypyrimidine tract binding protein (PTB), polypyrimidine-tract binding protein-associated factor (PSF), and non-POU-domain-containing, octamer-binding (NONO), DEAD (Asp-Glu-Ala-Asp) box polypeptide 5 (DDX5). U1A also binds to a flavivirus NS5 protein and plays an important role in virus replication. It contains two RNA recognition motifs (RRMs); the N-terminal RRM (RRM1) binds tightly and specifically to the U1 snRNA SLII and its own 3'-UTR, while in contrast, the C-terminal RRM (RRM2) does not appear to associate with any RNA and it may be free for binding other proteins. U1A also contains a proline-rich region, and a nuclear localization signal (NLS) in the central domain that is responsible for its nuclear import.

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gi 1033937341  80 ANPTID*PPNQILFLTNLPEET*E 103
Cdd:cd12480     2 PQPVSENPPNHILFLTNLPEETNE 25

RNA recognition motif 3 (RRM3) found in polypyrimidine tract-binding protein 1 (PTB or hnRNP I) and similar proteins; This subfamily corresponds to the RRM3 of polypyrimidine tract-binding protein 1 (PTB or hnRNP I), polypyrimidine tract-binding protein 2 (PTBP2 or nPTB), regulator of differentiation 1 (Rod1), and similar proteins found in Metazoa. PTB is an important negative regulator of alternative splicing in mammalian cells and also functions at several other aspects of mRNA metabolism, including mRNA localization, stabilization, polyadenylation, and translation. PTBP2 is highly homologous to PTB and is perhaps specific to the vertebrates. Unlike PTB, PTBP2 is enriched in the brain and in some neural cell lines. It binds more stably to the downstream control sequence (DCS) RNA than PTB does but is a weaker repressor of splicing in vitro. PTBP2 also greatly enhances the binding of two other proteins, heterogeneous nuclear ribonucleoprotein (hnRNP) H and KH-type splicing-regulatory protein (KSRP), to the DCS RNA. The binding properties of PTBP2 and its reduced inhibitory activity on splicing imply roles in controlling the assembly of other splicing-regulatory proteins. PTBP2 also contains four RRMs. ROD1 coding protein Rod1 is a mammalian PTB homolog of a regulator of differentiation in the fission yeast Schizosaccharomyces pombe, where the nrd1 gene encodes an RNA binding protein negatively regulates the onset of differentiation. ROD1 is predominantly expressed in hematopoietic cells or organs. It may play a role controlling differentiation in mammals. All members in this family contain four RNA recognition motifs (RRM), also known as RBD (RNA binding domain) or RNP (ribonucleoprotein domain).

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gi 1033937341   1 ALVVFREISSASNALRTMQGFPFYDKPMRIAYAK 34
Cdd:cd12423    40 ALIQMADPQQAQTALQHLNGIKLFGKPIRVTLSK 73

RNA recognition motif 2 (RRM2) found in RNA-binding protein 40 (RBM40) and similar proteins; This subfamily corresponds to the RRM2 of RBM40 and the RRM of RBM41. RBM40, also known as RNA-binding region-containing protein 3 (RNPC3) or U11/U12 small nuclear ribonucleoprotein 65 kDa protein (U11/U12-65K protein). It serves as a bridging factor between the U11 and U12 snRNPs. It contains two RNA recognition motifs (RRMs), also known as RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains), connected by a linker that includes a proline-rich region. It binds to the U11-associated 59K protein via its RRM1 and employs the RRM2 to bind hairpin III of the U12 small nuclear RNA (snRNA). The proline-rich region might be involved in protein-protein interactions. RBM41 contains only one RRM. Its biological function remains unclear.

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gi 1033937341   1 ALVVFREISSASNALRTMQGFPFYDKPMRIAYA 33
Cdd:cd12239    50 AFITFPSEELAEKALNLTNGYVLHGKPMVVQFA 82