SDS-PAGE analysis of KΔUL36 particles. HEL cells (2 × 107) infected with KOS and KΔUL36 at an MOI of 10 PFU/cell were labeled with [35S]methionine from 8 to 24 h after infection. Cell lysates were sedimented through 20 to 50% sucrose gradients, the light-scattering bands were harvested by side puncture, and the particles were pelleted and again sedimented through 20 to 50% sucrose gradients. Fractions collected after sedimentation were TCA precipitated, and the proteins in the fractions were resolved by SDS-PAGE (17% acrylamide). Fraction 1 corresponds to the bottom of the tube. Relevant virion proteins are indicated at the right; protein standards (lane M) correspond to 220, 97.4, 66, 46, 30, and 14.3 kDa (indicated by the closed circles).