N-terminal putative catalytic domain of uncharacterized HKD family nucleases fused to putative helicases from the Snf2-like family
N-terminal putative catalytic domain of uncharacterized archaeal and prokaryotic HKD family nucleases fused to putative helicases from the Snf2-like family, which belong to the DNA/RNA helicase superfamily II (SF2). Although Snf2-like family enzymes do not possess helicase activity, they contain a helicase-like region, where seven helicase-related sequence motifs are found, similar to those in DEAD/DEAH box helicases, which represent the biggest family within the SF2 superfamily. In addition to the helicase-like region, members of this family also contain an N-terminal putative catalytic domain with one copy of the conserved HKD motif (H-x-K-x(4)-D, where x represents any amino acid residue), and have been classified as members of the phospholipase D (PLD, EC 3.1.4.4) superfamily.
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