This is a PAZ domain is found in argonaute present in Thermus thermophiles. Argonaute has a central role in the RNA interference pathway by mediating the maturation of small interfering RNA (siRNA) through initial degradation of the passenger strand, followed by guide-strand-mediated sequence-specific cleavage of target mRNA. The nucleic-acid-binding channel is thought to be positioned between the PAZ and PIWI domain [1].

1: Structure of the guide-strand-containing argonaute silencing complex. Wang Y, Sheng G, Juranek S, Tuschl T, Patel DJ; Nature. 2008;456:209-213. PMID:18754009