Figure 2.Five major superfamilies of DNA helicases. The conserved signature amino acid sequence motifs are shown relative to the modular domains (shown as solid blocks) of helicases that belong to five major families. The motifs that are characteristic of all helicases within a particular superfamily are shown in black, while the motifs characteristic only to subsets of the SF2 helicases are represented by a hashed block. Alternative designations for some signature motifs are given in parentheses. In addition to the core domains containing the signature motifs, helicases frequently contain domains either adjacent to or inserted between the conserved motifs of the core domain. Examples of such domains are shown as discontinuous blocks. The areas containing large insertions that define additional enzymatic activities are indicated by broken lines. The oligomeric state and translocation polarity for each superfamily is indicated to the right of the block diagram.
