Structural Features
The common function of helicases accounts for the fact that they display a certain degree of amino acid sequence homology; they all possess common sequence motifs located in the interior of their primary structure. These are thought to be specifically involved in ATP binding, ATP hydrolysis and translocation on the nucleic acid substrate. The variable portion of the amino acid sequence is related to the specific features of each helicase.
Based on the presence of defined helicase motifs, it is possible to attribute a putative helicase activity to a given protein, though the presence of a motif does not confirm the protein as a helicase. Conserved motifs do, however, support an evolutionary homology among enzymes. Based on the presence and the form of helicase motifs, helicases have been separated in 4 superfamilies and 2 smaller families. Some members of these families are indicated, with the organism from which they are extracted, and their function.
Read more about this topic: Helicase
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