ribonucleoproteins |
Proteins conjugated with ribonucleic acids (RNA) or specific RNA. Many viruses are ribonucleoproteins. (12 Dec 1998) |
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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) |
ribonucleoside |
<biochemistry> A nucleoside in which purine or pyrimidine base is linked to a ribose molecule. (09 Oct 1997) |
ribonucleoside diphosphate reductase |
<enzyme> An enzyme of the oxidoreductase class that catalyses the formation of 2'-deoxyribonucleotides from the corresponding ribonucleotides using NADPH as the ultimate electron donor. The deoxyribonucleoside diphosphates are used in DNA synthesis. Chemical name: 2'-Deoxyribonucleoside-diphosphate:oxidised-thioredoxin 2'-oxidoreductase Registry number: EC 1.17.4.1 (12 Dec 1998) |
ribonucleoside-triphosphate reductase |
<enzyme> Requires a cobamide coenzyme and ATP Registry number: EC 1.17.4.2 Synonym: rtp reductase (26 Jun 1999) |
ribonucleosides |
Nucleosides in which the purine or pyrimidine base is combined with ribose. (12 Dec 1998) |
ribonucleotide |
<biochemistry> A nucleotide in whicha purine or pyrimidine base is linked to a ribose molecule. (09 Oct 1997) |
ribonucleotide polymerase |
<enzyme> DNA-dependent Registry number: EC 2.7.7.- Synonym: oligonucleotide polymerase, decaribonucleotide polymerase (26 Jun 1999) |
ribonucleotide reductase |
A protein complex that converts ribonucleotide diphosphates (NDPs) such as ADP and CDP to 2'-deoxyribonucleotide diphosphates (dNDPs) such as dADP and dCDP. This complex requires thioredoxin, thioredoxin reductase, and NADPH. It is crucial for DNA synthesis. (05 Mar 2000) |
ribonucleotide reductases |
<enzyme> Registry number: EC 1.17.4 (12 Dec 1998) |
ribonucleotides |
Nucleotides in which the purine or pyrimidine base is combined with ribose. (12 Dec 1998) |