Expression in Escherichia coli and purification of biologically active L proteinase of foot-and-mouth disease virus.

The foot-and-mouth disease virus (FMDV) Lb gene was cloned into bacterial expression vectors under the control of a T7 RNA polymerase promoter. The Lb protein was expressed in both an in vitro transcription-translation system and in Escherichia coli. In vitro expression of a construct containing the Lb gene fused to a portion of the VP4 and 3D genes demonstrated cis cleavage activity that could be blocked by the thiol protease inhibitor E-64. Lb expressed in E. coli was purified from the soluble fraction by metal chelation chromatography. Purified Lb had trans cleavage activity at the L/P1 junction and cleaved the p220 component of the cap-binding protein complex.