FIG. 4.

In vitro trans cleavage by recombinant PLP-1 is more efficient at room temperature. Radiolabeled viral polypeptides were synthesized in a coupled transcription-translation system using as templates pSPN₁S₁ (A) and pSPΔMscN₁S₁ (B). Viral substrates were incubated with recombinant MBP–PLP-1 fusion enzyme overnight at either 22°C (lane 1) or 30°C (lane 2), followed by electrophoresis on SDS–10% polyacrylamide gels. Cleavage products are indicated by the arrows. In panel B, cleavage at the p65 site generates the carboxyl-terminal p50 polypeptide. The molecular masses of marker proteins are indicated to the right of panel B.