Figure 6.

Two different mechanisms of regulation of the ϕ29 motor. Individual components of the packaging complex are labeled in Fig. 1. (A) Forces acting directly on the section of DNA that enters through the portal exert a direct load on the portion of the motor that grips and translocates the DNA (dashed circle). (B) DNA packaged inside the prohead interacts with the inner wall of the prohead and a portion of the portal protein that protrudes into the interior. This interaction allosterically regulates the motor protein attached to the exterior portion of the portal in a manner distinct from direct load. Images were constructed as described in Fig. 1.