FIG. 3.

Dec protein binds only expanded P22 coat protein shells. Purified C-terminally histidine-tagged Dec protein (lane marked Dec-HisC) was mixed with purified P22 procapsids (PC), expanded P22 procapsids (Exp PC), or P22 “empty heads” (EH). These particles were produced as described in Materials and Methods. After incubation of an excess of Dec protein with the particles in TM for 30 min at room temperature, the particles were pelleted through a 10% sucrose cushion at 30,000 rpm in a Beckman SW50.1 ultracentrifuge rotor for 2 h and resuspended in fresh TM. Unassembled Dec protein does not pellet under these conditions. The component proteins of the particles, before and after Dec protein treatment, are displayed in a 12.5% polyacrylamide-SDS electrophoresis gel that was stained with Coomassie brilliant blue. The labels on the right are the same as in Fig. 2, and gp8 is scaffolding protein.