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Figure 3 | Biology Direct

Figure 3

From: Functional insight into Maelstrom in the germline piRNA pathway: a unique domain homologous to the DnaQ-H 3'–5' exonuclease, its lineage-specific expansion/loss and evolutionarily active site switch

Figure 3

Sequence and structure similarity between MAEL and DnaQ-H domains. (A) Sequence and the secondary structure alignment of MAEL and DnaQ-H domains. Seven DnaQ-H domains are included and five domains have 3-D structures: Thermotaga maritime ε exonuclease (Tm ε, 2P1J:A), Escherichia coli ε exonuclease (Ec_ε, 1J53:A), Haemophilus influenzae oligoribonuclease (Hi_Orn, 1J9A:A), human Trex2 exonuclease (Hs_Trex2, 1Y97:A) and human 3’-5’ exoribonuclease (Hs_Exo, 1W0H:A). The conserved DnaQ-H specific residues (DEDHD) are highlighted with the blue background; whereas the conserved MAEL-specific residues (EHHCHC) are highlighted with the red background. The MAEL-specific residues (EHH) also exist at counterpart positions in some DnaQ-H domains, and were highlighted with pink background. Detailed secondary structures for MAEL domains and DnaQ-H domains are obtained from secondary structure predictions and the 3-D structures, respectively; they are shown below the alignment (h in red, α helix; e in blue, β sheet). The structural sequence alignment was established carefully by hand on the basis of CE-MC results, alignment in fold recognition, literature information, and predicted secondary structures. The numbers in bracket are indicative of the excluded residues from sequences. New species name abbreviations: Tm, Thermotaga maritime; Alteromonas macleodii; marine gamma proteobacterium. (B-E) NewCartoon diagrams for DnaQ-H domains (1J53:A and 1W0H:A) and the homology model of two MAEL domains (Eh 67476664 and chicken MAEL). The α helices are shown in pink, β sheets in yellow, and loops in white; Their spatial locations are labeled in 1J53:A. Strictly conserved DnaQ-H active site residues DEDHD of protist MAEL domain (Eh 67476664) are highlighted in licorice drawing with acidic residues (D and E) in red and basic His in blue. The MAEL-specific residues EHHCHC of chicken MAEL domain are highlighted with Glu in red, His in blue and Cys in orange.

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