Polynucleotide Phosphorylase
Structure of the PNPase trimer from Streptomyces antibioticus. PDB 1e3p.[1]
Identifiers
EC no.2.7.7.8
CAS no.9014-12-4
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO
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NCBIproteins

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]

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
SymbolPNPASE
Alt. symbolsPNPase, OLD35, old-35
NCBI gene87178
HGNC23166
OMIM610316
PDB1E3P
RefSeqNM_033109
UniProtQ8TCS8
Other data
EC number2.7.7.8
LocusChr. 2 p15
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StructuresSwiss-model
DomainsInterPro

References

  1. 1 2 3 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.
  2. 1 2 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.
  3. ↑ 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.
  4. ↑ 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.
  5. ↑ 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.
  6. ↑ 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.
  7. 1 2 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.
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