FIG. 14.

Locations of subdomains and motifs in the RecD protein. (A) Cartoon representation of the three-subdomain structure of RecD. The small alpha-helical N-terminal domain 1 (wheat) is responsible for contacts with the RecC protein. Subdomains 2 and 3 (green and red) form a tandem RecA fold and are equivalent to subdomains 1A and 2A of SF1 DNA helicases. The 5′ ssDNA tail (deep purple) is shown approaching these core helicase domains. A portion of the protein comprising residues 466 to 523 is not resolved in the structure. (B) Cartoon representation with the seven conserved helicase motifs indicated. (C) Surface representation colored as described above for A. (D) Surface representation colored as described above for B. Notice the location of the helicase motifs at the interface and top surface of the core helicase domains. Their general location is similar to that seen in the RecB protein. Two regions are shown for motif 1a. The lower patch (*) represents the motif as defined previously (223). However, these residues are poorly conserved in RecD, do not resemble a canonical motif 1a, and do not occupy a similar position to the motif 1a of other SF1 helicases. The upper patch of residues (L201 to A208) represents a strongly conserved region that occupies a position similar to that of motif 1a of other SF1 helicases.