| Product Name |
3′-phosphate/5′-hydroxy nucleic acid ligase |
| Example Structure |
 |
| Synonyms |
3′-P RNL, MXAN_0280, MXAN_4982, RNA-splicing ligase, rtcB, RtcB RNA ligase, Rtcb-1, RtcB1, Trl1, tRNA splicing ligase, tRNA-splicing ligase |
| EC Number |
6.5.1.8 |
| CAS Registry Number |
|
| Comments |
The enzyme is a GTP- and Mn2+-dependent 3′-5′ nucleic acid ligase with the ability to join RNA with 3′-phosphate or 2′,3′-cyclic-phosphate ends to RNA with 5′-hydroxy ends. It can also join DNA with 3′-phosphate ends to DNA with 5′-hydroxy ends, provided the DNA termini are unpaired [6]. The enzyme is found in members of all three kingdoms of life, and is essential in metazoa for the splicing of intron-containing tRNAs. The reaction follows a three-step mechanism with initial activation of the enzyme by GTP hydrolysis, forming a phosphoramide bond between the guanylate and a histidine residue. The guanylate group is transferred to the 3′-phosphate terminus of the substrate, forming the capped structure [DNA/RNA]-3′-(5′-diphosphoguanosine). When a suitable 5′-OH end is available, the enzyme catalyses an attack of the 5′-OH on the capped end to form a 3′-5′ phosphodiester splice junction, releasing the guanylate. When acting on an RNA 2′,3′-cyclic-phosphate, the enzyme cayalyses an additional reaction, hydrolysing the cyclic phosphate to a 3′-phosphate [9]. The metazoan enzyme requires activating cofactors in order to achieve multiple turnover catalysis [8]. |
| Cofactor |
Mn2+ |
| History |
|
| Reactions |
(1) (Ribonucleotide)(n)-3′-phosphate + 5′-hydroxy-(ribonucleotide)(m) + Gtp = (ribonucleotide)(n+m) + gmp + diphosphate. (2) (Ribonucleotide)(n)-2′,3′-cyclophosphate + 5′-hydroxy- (ribonucleotide)(m) + Gtp + H(2)O = (ribonucleotide)(n+m) + gmp + diphosphate (overall reaction). |
