| ribonuclease (pancreatic) | |
|---|---|
| ribonuclease D | <enzyme> An enzyme (endonuclease) that trims the extra 3' nucleotides from immature tRNA. (05 Mar 2000) |
| ribonuclease h, calf thymus | <enzyme> A ribonuclease that specifically cleaves the RNA moiety of RNA:DNA hybrids. It has been isolated from a wide variety of prokaryotic and eukaryotic organisms (particularly calf thymus) as well as retroviruses. Registry number: EC 3.1.26.4 (12 Dec 1998) |
| ribonuclease t1 | <enzyme> An enzyme catalyzing the endonucleolytic cleavage of RNA at the 3'-position of a guanylate residue. Chemical name: Ribonucleate 3'-guanylo-oligonucleotidohydrolase Registry number: EC 3.1.27.3 (12 Dec 1998) |
| ribonuclease, pancreatic | <enzyme> An enzyme that catalyses the endonucleolytic cleavage of pancreatic ribonucleic acids to 3'-phosphomono- and oligonucleotides ending in cytidylic or uridylic acids with 2',3'-cyclic phosphate intermediates. Registry number: EC 3.1.27.5 (12 Dec 1998) |
| ribonucleases | <enzyme> Enzymes that catalyze the hydrolysis of ester bonds within RNA. Registry number: EC 3.1.- (12 Dec 1998) |
| ribonucleic acid | <molecular biology> A nucleic acid found in all living cells. Plays a role in transferring information from DNA to the protein-forming system of the cell. (16 Dec 1997) |
| ribonucleinase | <biochemistry, enzyme, molecular biology> Widely distributed type of enzyme that cleaves RNA. May act as endonucleases or exonucleases depending upon the type of enzyme. Generally recognise target by tertiary structure rather than sequence. Ribonuclease E is involved in the formation of 5S ribosomal RNA from pre rRNA. Ribonuclease F is stimulated by interferons and cleaves viral and host RNA and thus inhibits protein synthesis. Ribonuclease H specifically cleaves an RNA base paired to a complementary DNA strand. Ribonuclease P is an endonuclease that generate t RNA from their precursor transcripts. Ribonuclease T is an endonuclease that removes the terminal AMP from the 3' CCA end of a nonaminoacylated tRNA. Ribonuclease T1 cleaves RNA specifically at guanosine residues. Ribonuclease TIII cleaves double stranded regions of RNA molecules. Acronym: RNase (23 Aug 1998) |
| ribonucleoprotein | <protein> Complexes of RNA and protein involved in a wide range of cellular processes. Besides ribosomes (with which ribonucleoprotein was originally almost synonymous), in eukaryotic cells both initial RNA transcripts in the nucleus (hnRNA) and cytoplasmic mRNAs exist as complexes with specific sets of proteins. Processing (splicing) of the former is carried out by small nuclear ribonucleoproteins (snRNP). Other examples are the signal recognition particle responsible for targetting proteins to endoplasmic reticulum and a complex involved in termination of transcription. Acronym: RNP (23 Aug 1998) |
| ribonucleoproteins | Proteins conjugated with ribonucleic acids (RNA) or specific RNA. Many viruses are ribonucleoproteins. (12 Dec 1998) |
| ribonucleoproteins, small nuclear | Highly conserved nuclear RNA-protein complexes that function in RNA processing in the nucleus, including pre-mRNA splicing and pre-mRNA 3'-end processing in the nucleoplasm. The u3 snrnp is localised in the nucleolus, where it aligns into base pairs with the 28s rrna precursor in a still unidentified region and functions in pre-rrna processing. The u7 snrnp aligns into base pairs with a conserved sequence in the 3'-end of histone pre-mRNA and is an essential cofactor for the cleavage that creates the mature nonadenylated 3'-end. (12 Dec 1998) |
| ribonucleoproteins, small, u1 | A nuclear RNA-protein complex that plays a role in RNA processing. In the nucleoplasm, the u1 snrnp along with other small ribonucleoproteins (u2, u4-u6, and u5) assemble into spliceosomes that remove introns from pre-mRNA by splicing. The u1 snrnp base pairs with conserved sequence motifs at the 5'-splice site and recognises both the 5'- and 3'-splice sites and may have a fundamental role in aligning the two sites for the splicing reaction. (12 Dec 1998) |
| ribonucleoproteins, small, u2 | A nuclear RNA-protein complex that plays a role in RNA processing. In the nucleoplasm, the u2 snrnp along with other small ribonucleoproteins (u1, u4-u6, and u5) assemble into spliceosomes that remove introns from pre-mRNA by splicing. The u2 snrnp base pairs with conserved sequence motifs at the branch point, which associates with a heat- and rnaase-sensitive factor in an early step of splicing. (12 Dec 1998) |
| ribonucleoproteins, small, u4-u6 | A nuclear RNA-protein complex that plays a role in RNA processing. In the nucleoplasm, the u4-u6 snrnp along with the u5 snrnp preassemble into a single 25s particle that binds to the u1 and u2 snrnps and the substrate to form mature spliceosomes. There is also evidence for the existence of individual u4 or u6 snrnps in addition to their organization as a u4-u6 snrnp. (12 Dec 1998) |
| ribonucleoproteins, small, u5 | A nuclear RNA-protein complex that plays a role in RNA processing. In the nucleoplasm, the u5 snrnp along with u4-u6 snrnp preassemble into a single 25s particle that binds to the u1 and u2 snrnps and the substrate to form mature spliceosomes. (12 Dec 1998) |