Species-specific substrate interaction of picornavirus 3C proteinase suballelic exchange mutants

The substrate recognition properties of the polio-virus type 1 and coxsackievirus B3 3C proteinases have been examined in vitro by allelic and suballelic exchange of 3C between the cloned virus genomes. The activity of the altered 3C proteinases was examined by translation of synthetic RNA in a rabbit reticulocyte lysate/HeLa cell extract translation system. Analysis of the subsequent processing of virus polyproteins by the altered 3C proteinases showed that all of the mutant proteinases maintained some catalytic activity. The disruption of polyprotein cleavages mediated by 3C followed a distinct pattern, suggesting a specific order of events in processing the polyprotein. Differences in cleavage activity of mutant proteinases when tested on coxsackievirus or poliovirus protein substrates suggest that, although structural elements throughout the proteinase play a role in efficient substrate utilization, the carboxyl-terminal region of the 3C proteinase contains elements most important in species-specific substrate recognition.