Helicase structure. The structure of the hexameric helicase from bacteriophage T7. One of the six subunits is shown in yellow with the P-loop NTPase shown in purple. The loops that participate in DNA binding are highlighted by a yellow oval. Notice that each subunit interacts closely with its neighbors and that the DNA-binding loops line the hole in the center of the structure.
[Drawn from 1E0K.pdb.]