FIG. 4.

Comparison of the effects of mutations in the first and second exons of ICP0 in the in vitro conjugation reaction. GST fusion proteins based on either GST-262 or GST-241 were purified after bacterial expression. The locations and phenotypes of the mutations are shown in Table 1. All the proteins had similar expression, solubility, and stability properties (data not shown). The products of the in vitro ubiquitin conjugation reaction using E1, ubiquitin, UbcH5a, and added GST fusion protein were detected by probing a Western blot with the antiubiquitin antibody P4D1.