Polynucleotide 5'-phosphatase explained
| polynucleotide 5′-phosphatase |
| Ec Number: | 3.1.3.33 |
| Cas Number: | 37288-17-8 |
| Go Code: | 0004651 |
The enzyme polynucleotide 5′-phosphatase (RNA 5′-triphosphatase, RTPase, EC 3.1.3.33) is an enzyme that catalyzes the reaction
a 5′-phosphopolynucleotide + H2O
a polynucleotide + phosphate
This enzyme belongs to the family of hydrolases, specifically those acting on phosphoric monoester bonds. The systematic name is polynucleotide 5′-phosphohydrolase. This enzyme is also called 5′-polynucleotidase.
The only specific molecular function known is the catalysis of the reaction:
a 5′-end triphospho-(purine-ribonucleotide) in mRNA + H2O = a 5′-end diphospho-(purine-ribonucleoside) in mRNA + phosphate
RTPases cleave the 5′-terminal γ-β phosphoanhydride bond of nascent messenger RNA molecules, enabling the addition of a five-prime cap as part of post-transcriptional modifications. RTPases generate 5′-diphosphate-ended mRNA and a phosphate ion from 5′-triphosphate-ended precursor mRNA. mRNA guanylyltransferase then adds a backwards guanosine monophosphate (GMP) group from GTP, generating pyrophosphate, and mRNA (guanine-N7-)-methyltransferase methylates the guanine to form the final 5′-cap structure.[1] [2] [3] [4] [5]
There are two families of RTPases known so far:
- the metal-dependent family. Yeast,[4] [6] [7] protozoan, and viral[4] [8] RTPases require a metal co-factor for their activity, which is most often either Mg2+ or Mn2+. This class of enzymes is also able to hydrolyze free nucleoside triphosphates in the presence of either Mn2+ or Co2+.[1]
- the metal-independent family. These groups do not require metals for their activity, and some enzymes have been shown to be inactivated in the presence of metal ions. These enzymes are very much similar to protein tyrosine phosphatases in their structure and mechanism.[9] [10] [11] This family includes RTPases from mammals, plants, and other higher eukaryotes,[8] and is structurally and mechanistically different from the metal-dependent RTPase family.[4] [5] [7]
Structural studies
As of late 2007, 5 structures have been solved for this class of enzymes, with PDB accession codes,,,, and .
See also
Further reading
- Becker A, Hurwitz J . The enzymatic cleavage of phosphate termini from polynucleotides . The Journal of Biological Chemistry . 242 . 5 . 936–50 . March 1967 . 10.1016/S0021-9258(18)96215-0 . 4289819 . free .
Notes and References
- Gross CH, Shuman S . Characterization of a baculovirus-encoded RNA 5′-triphosphatase . Journal of Virology . 72 . 9 . 7057–63 . September 1998 . 9696798 . 10.1128/JVI.72.9.7057-7063.1998 . 109926 . free .
- Ho CK, Schwer B, Shuman S . Genetic, physical, and functional interactions between the triphosphatase and guanylyltransferase components of the yeast mRNA capping apparatus . Molecular and Cellular Biology . 18 . 9 . 5189–98 . September 1998 . 9710603 . 109104 . 10.1128/MCB.18.9.5189 .
- Shuman S . Structure, mechanism, and evolution of the mRNA capping apparatus . Progress in Nucleic Acid Research and Molecular Biology . 66 . 1–40 . 2000 . 11051760 . 10.1016/s0079-6603(00)66025-7 . 9780125400664 .
- Takagi T, Moore CR, Diehn F, Buratowski S . An RNA 5′-triphosphatase related to the protein tyrosine phosphatases . Cell . 89 . 6 . 867–73 . June 1997 . 9200605 . 10.1016/S0092-8674(00)80272-X . 10484079 . free .
- Wen Y, Yue Z, Shatkin AJ . Mammalian capping enzyme binds RNA and uses protein tyrosine phosphatase mechanism . Proceedings of the National Academy of Sciences of the United States of America . 95 . 21 . 12226–31 . October 1998 . 9770468 . 22813 . 10.1073/pnas.95.21.12226 . 1998PNAS...9512226W . free .
- Bisaillon M, Bougie I . Investigating the role of metal ions in the catalytic mechanism of the yeast RNA triphosphatase . The Journal of Biological Chemistry . 278 . 36 . 33963–71 . September 2003 . 12819229 . 10.1074/jbc.M303007200 . free .
- Lima CD, Wang LK, Shuman S . Structure and mechanism of yeast RNA triphosphatase: an essential component of the mRNA capping apparatus . Cell . 99 . 5 . 533–43 . November 1999 . 10589681 . 10.1016/S0092-8674(00)81541-X . 1785538 . free .
- Karpe YA, Lole KS . RNA 5'-triphosphatase activity of the hepatitis E virus helicase domain . Journal of Virology . 84 . 18 . 9637–41 . September 2010 . 20592074 . 2937651 . 10.1128/JVI.00492-10 .
- Barford D, Flint AJ, Tonks NK . Crystal structure of human protein tyrosine phosphatase 1B . Science . 263 . 5152 . 1397–404 . March 1994 . 8128219 . 10.1126/science.8128219 . 1994Sci...263.1397B .
- Denu JM, Dixon JE . Protein tyrosine phosphatases: mechanisms of catalysis and regulation . Current Opinion in Chemical Biology . 2 . 5 . 633–41 . October 1998 . 9818190 . 10.1016/S1367-5931(98)80095-1 .
- Deshpande T, Takagi T, Hao L, Buratowski S, Charbonneau H . Human PIR1 of the protein-tyrosine phosphatase superfamily has RNA 5'-triphosphatase and diphosphatase activities . The Journal of Biological Chemistry . 274 . 23 . 16590–4 . June 1999 . 10347225 . 10.1074/jbc.274.23.16590 . free .
