Ribonuclease Article Index for
Ribonuclease 		 

Information About

Ribonuclease
  CATEGORIES ABOUT RIBONUCLEASE
   
ribonucleases
   
ec 3.1
   
ec 3.1.26
   
ec 3.1.27
   
APPAREL
BABY
BEAUTY
BOOKS
CAR TOYS
CELL PHONES
DVD'S
ELECTRONICS
GOURMET FOOD
GROCERIES
HEALTH & PERSONAL
HOME & GARDEN
JEWELRY
MUSIC
MUSIC INSTRUMENTS
OFFICE PRODUCTS
SOFTWARE
SPORTING GOODS
TOOLS & HARDWARE
TOYS
VIDEO GAMES
SHOPPING HOME
MORE SHOPPING...




FUNCTION

RNases are extremely common, resulting in very short lifespans for any RNA that is not in a protected environment. One mechanism of protection is Ribonuclease Inhibitor (RI), which comprises a relatively large fraction of cellular protein (~0.1%) and which binds to certain ribonucleases with the highest affinity of any Protein-protein Interaction ; the Dissociation Constant for the RI-RNase A complex is ~20 fM under physiological conditions. RI is used in most laboratories that study RNA to protect their samples against degradation from environmental RNases.

Perhaps surprisingly, RNases tend to be insensitive to the cleaved sequence. There appear to be no RNase analogs of the Restriction Enzyme s, which cleave highly specific sequences of double-stranded DNA . This deficit may be overcome using RNase H and single-stranded DNA complementary to the desired cleavage sequence.

RNases play a critical role in many biological processes, including Angiogenesis and Self-incompatibility in
Flowering Plant s (angiosperms).


CLASSIFICATION


Major types of endoribonucleases


  • : '''. It is sequence specific for single stranded RNAs. It cleaves 3'end of unpaired C and U residues, leaving a 3'-phosphorylated product.


  • : RNase P is a type of ribonuclease and is currently under heavy research. RNase P is unique from other RNases in that it is a Ribozyme – a Ribonucleic Acid that acts as a catalyst in the same way that a Protein based enzyme would. Its function is to cleave off an extra, or precursor, sequence of RNA on TRNA molecules. Further RNase P is one of two known multiple turnover ribozymes in nature (the other being the Ribosome ).


  • : RNase H is a ribonuclease that cleaves the RNA in a DNA/RNA duplex to produce ssDNA. RNase H is a non-specific endonuclease and catalyzes the cleavage of RNA via a hydrolytic mechanism, aided by an enzyme-bound divalent metal ion. RNase H leaves a 5'-phosphorylated product.


  • : RNase III is a type of ribonuclease that cleaves rRNA (16s rRNA and 23s rRNA) from transcribed polycistronic RNA operon in prokaryotes.


  • : RNase T1 is sequence specific for single stranded RNAs. It cleaves 3'-end of unpaired G residues.


  • : RNase T2 is sequence specific for single stranded RNAs. It cleaves 3'-end of all 4 residues, but preferentially 3'-end of As.


  • : RNase U2 is sequence specific for single stranded RNAs. It cleaves 3'-end of unpaired A residues.


  • : RNase V1 is non-sequence specific for double stranded RNAs. It cleaves base-paired nucleotide residues.


  • ''' cleaves 3'-end of all 4 residues with no base preference


  • ''' is an interferon-induced nuclease which, upon activation, destroys all RNA within the cell


  • ''' is sequence specific for single stranded RNAs. It cleaves 3'-end of unpaired A and U residues.




Major types of exoribonucleases



  • ''' is responsible for the processive 3'-to-5' degradation of single-stranded RNA .


  • ''' is a close homolog of RNase II, but it can, unlike RNase II, degrade RNA with secondary structures without help of accessory factors.


  • ''' is involved in the 3'-to-5' processing of pre- TRNA s.


  • ''' is the major contributor for the 3'-to-5' maturation of many stable RNAs.



  • : Exoribonuclease I degrades single-stranded RNA from 5'-to-3', exists only in eukaryotes.




EXTERNAL LINKS





REFERENCES


  • D'Alessio G and Riordan JF, eds. (1997) ''Ribonucleases: Structures and Functions'', Academic Press.