Exoribonuclease II

Exoribonuclease II (also known as RNase R) is an enzyme that plays a crucial role in RNA degradation and turnover in both prokaryotic and eukaryotic organisms. It is a highly processive 3'-to-5' exoribonuclease that degrades RNA molecules in a non-sequence-specific manner. This article will provide an overview of Exoribonuclease II, its structure, function, and biological significance.

Structure

Exoribonuclease II is a conserved enzyme found in various organisms, including bacteria, archaea, and eukaryotes. In bacteria, it is encoded by the rnr gene. The enzyme consists of a single polypeptide chain with a molecular weight of approximately 100 kDa. It contains several conserved domains, including an N-terminal S1 RNA-binding domain and a C-terminal catalytic domain. The S1 domain is responsible for binding to RNA substrates, while the catalytic domain carries out the enzymatic activity.

Function

Exoribonuclease II is primarily involved in RNA degradation and turnover processes. It acts on a wide range of RNA molecules, including messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA), and small non-coding RNAs. The enzyme degrades RNA molecules in the 3'-to-5' direction, removing nucleotides one by one. This process helps maintain cellular homeostasis by eliminating unwanted or damaged RNA molecules.

Biological Significance

Exoribonuclease II plays a crucial role in various biological processes. In bacteria, it is involved in the degradation of mRNA molecules, which helps regulate gene expression and control the abundance of specific transcripts. Additionally, Exoribonuclease II is essential for the quality control of RNA molecules, ensuring that only functional and intact RNAs are present in the cell. In eukaryotes, the enzyme is involved in RNA surveillance pathways, such as the degradation of aberrant or non-functional RNAs.

Role in RNA Decay Pathways

Exoribonuclease II is a key player in several RNA decay pathways. In bacteria, it works in conjunction with other enzymes, such as polynucleotide phosphorylase (PNPase) and ribonuclease E (RNase E), to degrade mRNA molecules. The coordinated action of these enzymes ensures efficient and accurate RNA decay. In eukaryotes, Exoribonuclease II participates in the cytoplasmic RNA decay pathway, which involves the degradation of cytoplasmic mRNAs that are no longer needed or have become defective.

References

1. RNase R on Wikipedia 2. RNA degradation on Wikipedia

See Also

• Ribonuclease
• RNA-binding proteins
• RNA processing
• RNA surveillance