SMART accession number:SM00950
Description: This domain is found in the protein Piwi and its relatives. The function of this domain is the dsRNA guided hydrolysis of ssRNA. Determination of the crystal structure of Argonaute reveals that PIWI is an RNase H domain, and identifies Argonaute as Slicer, the enzyme that cleaves mRNA in the RNAi RISC complex (PUBMED:15284453) . In addition, Mg+2 dependence and production of 3'-OH and 5' phosphate products are shared characteristics of RNaseH and RISC. The PIWI domain core has a tertiary structure belonging to the RNase H family of enzymes. RNase H fold proteins all have a five-stranded mixed beta-sheet surrounded by helices. By analogy to RNase H enzymes which cleave single-stranded RNA guided by the DNA strand in an RNA/DNA hybrid, the PIWI domain can be inferred to cleave single-stranded RNA, for example mRNA, guided by double stranded siRNA.
Interpro abstract (IPR003165):

This domain is found in the stem cell self-renewal protein Piwi and its relatives in Drosophila melanogaster [(PUBMED:9851978)]. It has been found in the C-terminal of a number of proteins which also contain the PAZ domain (IPR003100) in their central region, for example the Argonaute proteins. Several of these proteins have been implicated in the development and maintenance of stem cells through the RNA-mediated gene-quelling mechanisms associated with the protein DICER.

GO function:protein binding (GO:0005515)
Family alignment:
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There are 2931 Piwi domains in 2925 proteins in SMART's nrdb database.

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