Exoribonuclease

Source: Wikipedia, the free encyclopedia.
Reaction diagrams for both hydrolytic (left) and phosphorolytic (right) 3'-5' exoribonuclease degradation of RNA.

An exoribonuclease is an

3' end
of the RNA molecule. Enzymes that remove nucleotides from the 5' end are called 5'-3' exoribonucleases, and enzymes that remove nucleotides from the 3' end are called 3'-5' exoribonucleases.

Exoribonucleases can use either water to cleave the nucleotide-nucleotide bond (which is called hydrolytic activity) or

inorganic phosphate (which is called phosphorolytic activity). Hydrolytic exoribonucleases are classified under EC number 3.1 and phosphorolytic exoribonucleases under EC number 2.7.7. As the phosphorolytic enzymes use inorganic phosphate to cleave bonds they release nucleotide diphosphates, whereas the hydrolytic enzymes (which use water) release nucleotide monosphosphates
.

Exoribonucleases exist in all kingdoms of life, the

miRNA. Exoribonucleases can be single proteins (such as RNase D or RNase PH) but also can be complexes of multiple proteins, such as the exosome complex
(in which four of the major exoribonuclease families are represented).

Major families

Family Example members Distribution Catalytic activity
RNR RNase R Most bacteria, all eukaryotes 3'-5' hydrolytic
RNase II
Rrp44
DEDD RNase D Certain bacteria, all eukaryotes 3'-5' hydrolytic
RNase T
PM/Scl-100
Oligoribonuclease
RBN RNase BN Certain bacteria 3'-5' hydrolytic
PDX
PNPase
All kingdoms 3'-5' phosphorolytic
PM/Scl-75
RNase PH
RRP4 Rrp4 All eukaryotes, most archaea 3'-5' hydrolytic
5PX
Exoribonuclease I
All eukaryotes 5'-3' hydrolytic
Exoribonuclease II

See also

References

  • Zuo Y; Deutscher MP. (2001). "Exoribonuclease superfamilies: structural analysis and phylogenetic distribution". Nucleic Acids Res. 29 (5): 1017–26.
    PMID 11222749
    .

External links