IN-VITRO ASSEMBLY OF COWPEA CHLOROTIC MOTTLE VIRUS FROM COAT PROTEIN EXPRESSED IN ESCHERICHIA-COLI AND IN VITRO-TRANSCRIBED VIRAL CDNA

The small spherical plant virus, cowpea chlorotic mottle virus (CCMV), provides an ideal system to examine spherical virus assembly. We have modified the CCMV in vitro assembly system to produce virions from co at protein expressed in Escherichia coil and viral RNA transcribed in vitro from full-length cDNAs. Examination of the in vitro-assembled pa rticles with cryoelectron microscopy and image reconstruction techniqu es demonstrates that the particles are indistinguishable from plant pu rified particles at 2.5 nm resolution. Mutational analysis of the coat protein N- and C-terminal extensions demonstrate their respective rol es in virus assembly. The N-terminus is required for assembly of RNA c ontaining particles but not for the assembly of empty virions. The C-t erminus is essential for coat protein dimer formation and particle ass embly. (C) 1995 Academic Press, Inc.