Polynucleotide Phosphorylase (PNPase) is a bifunctional enzyme with a phosphorolytic 3' to 5' exoribonuclease activity and a 3'-terminal oligonucleotide polymerase activity.[2] That is, it dismantles the RNA chain starting at the 3' end and working toward the 5' end.[1] It also synthesizes long, highly heteropolymeric tails in vivo. It accounts for all of the observed residual polyadenylation in strains of Escherichia coli missing the normal polyadenylation enzyme.[1] Discovered by Marianne Grunberg-Manago working in Severo Ochoa's lab in 1955, the RNA-polymerization activity of PNPase was initially believed to be responsible for DNA-dependent synthesis of messenger RNA, a notion that was disproven by the late 1950s.[3][4]
| Polynucleotide Phosphorylase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 | |||||||||
| Identifiers | |||||||||
| EC no. | 2.7.7.8 | ||||||||
| CAS no. | 9014-12-4 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / QuickGO | ||||||||
| |||||||||
It is involved in mRNA processing and degradation in bacteria, plants,[5] and animals.[6]
In humans, the enzyme is encoded by the PNPT1 gene. In its active form, the protein forms a ring structure consisting of three PNPase molecules. Each PNPase molecule consists of two RNase PH domains, an S1 RNA binding domain and a K-homology domain. The protein is present in bacteria and in the chloroplasts[2] and mitochondria[7] of some eukaryotic cells. In eukaryotes and archaea, a structurally and evolutionary related complex exists, called the exosome complex.[7]
The same abbreviation (PNPase) is also used for another, otherwise unrelated enzyme, Purine nucleoside phosphorylase.
| Human PNPase I | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Symbol | PNPASE | ||||||
| Alt. symbols | PNPase, OLD35, old-35 | ||||||
| NCBI gene | 87178 | ||||||
| HGNC | 23166 | ||||||
| OMIM | 610316 | ||||||
| PDB | 1E3P | ||||||
| RefSeq | NM_033109 | ||||||
| UniProt | Q8TCS8 | ||||||
| Other data | |||||||
| EC number | 2.7.7.8 | ||||||
| Locus | Chr. 2 p15 | ||||||
| |||||||
References
edit- ^ a b c Symmons MF, Jones GH, Luisi BF (November 2000). "A duplicated fold is the structural basis for polynucleotide phosphorylase catalytic activity, processivity, and regulation". Structure. 8 (11): 1215–26. doi:10.1016/S0969-2126(00)00521-9. PMID 11080643.
- ^ a b Yehudai-Resheff S, Hirsh M, Schuster G (August 2001). "Polynucleotide phosphorylase functions as both an exonuclease and a poly(A) polymerase in spinach chloroplasts". Molecular and Cellular Biology. 21 (16): 5408–16. doi:10.1128/MCB.21.16.5408-5416.2001. PMC 87263. PMID 11463823.
- ^ Grunberg-Manago M, Ortiz PJ, Ochoa S (April 1956). "Enzymic synthesis of polynucleotides. I. Polynucleotide phosphorylase of azotobacter vinelandii". Biochimica et Biophysica Acta. 20 (1): 269–85. doi:10.1016/0006-3002(56)90286-4. PMID 13315374.
- ^ Furth JJ, Hurwitz J, Anders M (August 1962). "The role of deoxyribonucleic acid in ribonucleic acid synthesis. I. The purification and properties of ribonucleic acid polymerase" (PDF). The Journal of Biological Chemistry. 237 (8): 2611–9. doi:10.1016/S0021-9258(19)73796-X. PMID 13895983.
- ^ Yehudai-Resheff S, Zimmer SL, Komine Y, Stern DB (March 2007). "Integration of chloroplast nucleic acid metabolism into the phosphate deprivation response in Chlamydomonas reinhardtii". The Plant Cell. 19 (3): 1023–38. doi:10.1105/tpc.106.045427. PMC 1867357. PMID 17351118.
- ^ Sarkar D, Fisher PB (May 2006). "Human polynucleotide phosphorylase (hPNPase old-35): an RNA degradation enzyme with pleiotrophic biological effects" (PDF). Cell Cycle. 5 (10): 1080–4. doi:10.4161/cc.5.10.2741. PMID 16687933. S2CID 42371805.
- ^ a b Schilders G, van Dijk E, Raijmakers R, Pruijn GJ (2006). Cell and molecular biology of the exosome: how to make or break an RNA. International Review of Cytology. Vol. 251. pp. 159–208. doi:10.1016/S0074-7696(06)51005-8. ISBN 9780123646552. PMID 16939780.
External links
edit- Polynucleotide+Phosphorylase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
