MATERIALS AND METHODS
Preparation of Cell Extracts and Virus. KB cells were grown
and infected with Ad2 as described (7). "Late" infected cell extracts
were labeled with [35S]methionine (40 p.Ci/ml; 954 CiY
mmol; 1 Ci = 3.7 x 1010 becquerels; New England Nuclear)
from 15 to 21 hr after infection. "Early" infected cell extracts
were prepared by using cycloheximide (CHX) and arabinosylcytosine
(AraC) as described (8). 32P-Labeled extracts were prepared
by labeling cells with inorganic 32P04 (1 mCi/ml; carrierfree;
New England Nuclear). Cell pellets (4 x 107 cells) were
prepared according to the method of O'Farrell (1). Ad2 virions
labeled with [35S]methionine were purified as reported (7).
Protein concentration was estimated by the method of Lowry
et al. (9).
ID and 2D Gel Electrophoresis. For ID gels, extracts containing
5 X 105 cpm or 150 pAg of protein were applied per
lane. For 2D gels, 5 x 106 cpm or 600 Ag ofprotein was used.
[35S]Methionine-labeled (2 x 10" cpm) virion was applied to
both ID and 2D gels. '4C-Labeled proteins were used as molecular
weight markers (New England Nuclear). ID gels and the