X8 domain. The X8 domain domain contains at least 6 conserved cysteine residues that presumably form three disulphide bridges. The domain is found in an Olive pollen allergen as well as at the C-terminus of several families of glycosyl hydrolases. This domain may be involved in carbohydrate binding. This domain is characteristic of GPI-anchored domains.

RNA recognition motif in Drosophila melanogaster RNA-binding protein cabeza and similar proteins. This subgroup corresponds to the RRM in cabeza, also termed P19, or sarcoma-associated RNA-binding fly homolog (SARFH). It is a putative homolog of human RNA-binding proteins FUS (also termed TLS or Pigpen or hnRNP P2), EWS (also termed EWSR1), TAF15 (also termed hTAFII68 or TAF2N or RPB56), and belongs to the of the FET (previously TET) (FUS/TLS, EWS, TAF15) family of RNA- and DNA-binding proteins whose expression is altered in cancer. It is a nuclear RNA binding protein that may play an important role in the regulation of RNA metabolism during fly development. Cabeza contains one RNA recognition motif (RRM), also termed RBD (RNA binding domain) or RNP (ribonucleoprotein domain).

Possibly involved in carbohydrate binding. The X8 domain, which may be involved in carbohydrate binding, is found in an Olive pollen antigen as well as at the C terminus of family 17 glycosyl hydrolases. It contains 6 conserved cysteine residues which presumably form three disulfide bridges.

RNA recognition motif in the FET family of RNA-binding proteins. This subfamily corresponds to the RRM of FET (previously TET) (FUS/TLS, EWS, TAF15) family of RNA-binding proteins. This ubiquitously expressed family of similarly structured proteins predominantly localizing to the nuclear, includes FUS (also known as TLS or Pigpen or hnRNP P2), EWS (also known as EWSR1), TAF15 (also known as hTAFII68 or TAF2N or RPB56), and Drosophila Cabeza (also known as SARFH). The corresponding coding genes of these proteins are involved in deleterious genomic rearrangements with transcription factor genes in a variety of human sarcomas and acute leukemias. All FET proteins interact with each other and are therefore likely to be part of the very same protein complexes, which suggests a general bridging role for FET proteins coupling RNA transcription, processing, transport, and DNA repair. The FET proteins contain multiple copies of a degenerate hexapeptide repeat motif at the N-terminus. The C-terminal region consists of a conserved nuclear import and retention signal (C-NLS), a putative zinc-finger domain, and a conserved RNA recognition motif (RRM), also known as RBD (RNA binding domain) or RNP (ribonucleoprotein domain), which is flanked by 3 arginine-glycine-glycine (RGG) boxes. FUS and EWS might have similar sequence specificity; both bind preferentially to GGUG-containing RNAs. FUS has also been shown to bind strongly to human telomeric RNA and to small low-copy-number RNAs tethered to the promoter of cyclin D1. To date, nothing is known about the RNA binding specificity of TAF15.

Glycosyl hydrolases family 17.