Figure 1.

Phylogenetic conservation of Argonaute proteins in various organisms. (a) Phylogenetic tree of Argonaute proteins based on the protein sequence. Alignments of protein sequences were made with ClustalW and the tree built with TreeTop. (b) The corresponding domain organizations of the proteins listed in the tree, showing the PAZ (orange) and PIWI (red) domains. PIWI domains of slicer-active Ago proteins are in dark red; PIWI domains of inactive Ago proteins are in light red. (c) Catalytic residues of the PIWI domain in single-letter amino-acid code. D, aspartic acid; G, glycine; H, histidine; K, lysine. The sequences used in the alignment are Homo sapiens (Hs) Ago1 (NP_036331), Ago2 (NP_036286), Ago3 (NP_079128), Ago4 (NP_060099), Hili (NP_060538), Hiwi (NP_004755) Hiwi2 (NP_689644), Hiwi3 (NP_001008496); Drosophila melanogaster (Dm) Ago1 (NP_725341), Ago2 (NP_730054), Ago3 (ABO27430), Aubergine (CAA64320), PIWI (NP_476875); Arabidopsis thaliana (At) Ago1 (NP_849784), Ago2 (NP_174413), Ago3 (NP_174414), Ago4 (NP_565633), Ago5 (At2g27880), Ago6 (At2g32940), Ago7 (NP_177103), Ago8 (NP_197602), Ago9 (CAD66636), Ago10 (NP_199194); Shizosaccharomyces pombe (Sp) Ago (NP_587782) and Caenorhabiditis elegans (Ce) Alg-1 (NP_510322), Alg-2 (NP_871992). Accession numbers are for GenBank.