Polynucleotide phosphorylase explained

Polynucleotide Phosphorylase
Ec Number:2.7.7.8
Cas Number:9014-12-4
Go Code:0004654

Polynucleotide Phosphorylase (PNPase) is a bifunctional enzyme with a phosphorolytic 3' to 5' exoribonuclease activity and a 3'-terminal oligonucleotide polymerase activity.[1] That is, it dismantles the RNA chain starting at the 3' end and working toward the 5' end. 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. 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.[2] [3]

It is involved in mRNA processing and degradation in bacteria, plants,[4] and animals.[5]

In humans, the enzyme is encoded by the 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[1] and mitochondria[6] of some eukaryotic cells. In eukaryotes and archaea, a structurally and evolutionary related complex exists, called the exosome complex.[6]

The same abbreviation (PNPase) is also used for another, otherwise unrelated enzyme, Purine nucleoside phosphorylase.

Human PNPase I
Width:220
Hgncid:23166
Symbol:PNPASE
Altsymbols:PNPase, OLD35, old-35
Entrezgene:87178
Omim:610316
Refseq:NM_033109
Uniprot:Q8TCS8
Pdb:1E3P
Ecnumber:2.7.7.8
Chromosome:2
Arm:p
Band:15

Notes and References

  1. Yehudai-Resheff S, Hirsh M, Schuster G . Polynucleotide phosphorylase functions as both an exonuclease and a poly(A) polymerase in spinach chloroplasts . Molecular and Cellular Biology . 21 . 16 . 5408–16 . August 2001 . 11463823 . 87263 . 10.1128/MCB.21.16.5408-5416.2001 .
  2. Grunberg-Manago M, Ortiz PJ, Ochoa S . Enzymic synthesis of polynucleotides. I. Polynucleotide phosphorylase of azotobacter vinelandii . Biochimica et Biophysica Acta . 20 . 1 . 269–85 . April 1956 . 13315374 . 10.1016/0006-3002(56)90286-4.
  3. Furth JJ, Hurwitz J, Anders M . The role of deoxyribonucleic acid in ribonucleic acid synthesis. I. The purification and properties of ribonucleic acid polymerase . The Journal of Biological Chemistry . 237 . 2611–9 . August 1962 . 8 . 10.1016/S0021-9258(19)73796-X . 13895983 . free .
  4. Yehudai-Resheff S, Zimmer SL, Komine Y, Stern DB . Integration of chloroplast nucleic acid metabolism into the phosphate deprivation response in Chlamydomonas reinhardtii . The Plant Cell . 19 . 3 . 1023–38 . March 2007 . 17351118 . 1867357 . 10.1105/tpc.106.045427 .
  5. Sarkar D, Fisher PB . Human polynucleotide phosphorylase (hPNPase old-35): an RNA degradation enzyme with pleiotrophic biological effects . Cell Cycle . 5 . 10 . 1080–4 . May 2006 . 16687933 . 10.4161/cc.5.10.2741 . 42371805 . free .
  6. Book: Schilders G, van Dijk E, Raijmakers R, Pruijn GJ . Cell and molecular biology of the exosome: how to make or break an RNA . 251 . 159–208 . 2006 . 16939780 . 10.1016/S0074-7696(06)51005-8 . 9780123646552 . International Review of Cytology .