FIG. 6.

Two-dimensional phosphopeptide analysis of ICP27 phosphorylated in vitro with purified PKA catalytic subunit, CKII, or PKC. Immunoprecipitated ICP27 from virus-infected cells was first dephosphorylated by AP in vitro, then phosphorylated with PKA (A), CKII (B), or PKC (C) in the presence of [γ-³²P]ATP as shown in Fig. 5C, and finally subjected to two-dimensional tryptic phosphopeptide mapping as described in the legend to Fig. 3. Autoradiography was performed with intensifying screens. Arrowheads indicate the sample origins on TLC plates. Major phosphopeptides are identified by numbers, and unique peptides are indicated by asterisks (see the text).