DEXDc

DEAD-like helicases superfamily
DEXDc
SMART accession number:SM00487
Description:
Interpro abstract (IPR014001):

Helicases have been classified in 5 superfamilies (SF1-SF5). All of the proteins bind ATP and, consequently, all of them carry the classical Walker A (phosphate-binding loop or P-loop) and Walker B (Mg2+-binding aspartic acid) motifs. For the two largest groups, commonly referred to as SF1 and SF2, a total of seven characteristic motifs has been identified [(PUBMED:2546125)]. These two superfamilies encompass a large number of DNA and RNA helicases from archaea, eubacteria, eukaryotes and viruses that seem to be active as monomers or dimers. RNA and DNA helicases are considered to be enzymes that catalyse the separation of double-stranded nucleic acids in an energy-dependent manner [(PUBMED:11839499)].

The various structures of SF1 and SF2 helicases present a common core with two alpha-beta RecA-like domains [(PUBMED:11839499), (PUBMED:11087862)]. The structural homology with the RecA recombination protein covers the five contiguous parallel beta strands and the tandem alpha helices. ATP binds to the amino proximal alpha-beta domain, where the Walker A (motif I) and Walker B (motif II) are found. The N-terminal domain also contains motif III (S-A-T) which was proposed to participate in linking ATPase and helicase activities. The carboxy-terminal alpha-beta domain is structurally very similar to the proximal one even though it is bereft of an ATP-binding site, suggesting that it may have originally arisen through gene duplication of the first one.

This entry represents the DNA-binding domain of classical SF1 and SF2 helicases.

Family alignment:
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There are 43042 DEXDc domains in 42714 proteins in SMART's nrdb database.

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