Argonaute

Argonauts proteins are a family of proteins whose representatives are strongly conserved. They occur in almost all organisms, where they play an important role in the activation and regulation of genes.

Argonauts proteins are approximately 100 kDa, mainly basic proteins consisting of subunits PAZ and PIWI. The PAZ domain consists of 130 amino acids, and can also be found in the protein Dicer. It binds the targetierende si / miRNA and possibly serves as a protein-protein interaction domain to the endonuclease Dicer. The C-terminal PIWI domain has the Mg2 -dependent endonuclease activity against the substrate to be cut - mRNA. A classification of the Argonauts proteins occurs due to similarities in protein sequence into three classes:

• Argonaute - like protein → similar to Arabidopsis thaliana protein AGO1
• PIWI - like protein → strong relationship with PIWI protein from Drosophila melanogaster
• Group 3 Argonautes → recently discovered group of Argonauts proteins in Caenorhabditis elegans

Representatives of the AGO family of RNA -interference reactions ( RNAi), the microRNA -induced mRNA degradation, and post- transcriptional gene silencing ( PTGS) of the plant world involved. Argonauts proteins are part of the so-called RNA-induced silencing -complex (RISC ), which in RNA interference plays a central role. Ago2 binds the small- interfering - RNA portion (siRNA ), first intersects the non- complementary strand be targeted and - after successful bond - the substrate mRNA.

Depending on the system surveyed, form Argonauts proteins a priori complexes with DICER, in maximum description are DICER, TRBP, Ago2 as a protein complex of RISC before, after section of the dsRNA (RNAi ) or pre-miRNA dissoziiere DICER from the now active RISC.

Depending on the organism 's genome encodes 5 (eg fruit flies ), 8 ( eg, human ) or even up to 27 (eg, Caenorhabditis elegans) Argonauts proteins. However, there are also organisms, such as the parasite Trypanosoma cruzi, which has placed its entire RNAi machinery in the course of evolution, and only catalytically inactive owns AGO proteins.