“…The PIWI-like domain is thought to possess the catalytic ability to degrade target DNA or RNA due to the conserved tetrad catalytic center [ 20 ]. All of the currently described dead TtAgo mutations are located in the PIWI-like domain, such as the two symmetrical arginine residues (R545, involved in the cleavage reaction, and R486, not involved in target cleavage), which play distinct roles in ssDNA target cleavage [ 48 ], and TtAgoDM (Double mutant; D478A, D546A), which showed no cleavage activity in in vitro cleavage assay [ 31 ]. Surprisingly, no mutations within the PIWI domain were isolated in our high-throughput screen.…”