M. Klikova et al., EFFICIENT IN-VIVO AND IN-VITRO ASSEMBLY OF RETROVIRAL CAPSIDS FROM GAG PRECURSOR PROTEINS EXPRESSED IN BACTERIA, Journal of virology, 69(2), 1995, pp. 1093-1098
The capsid precursor protein (Gag) of Mason-Pfizer monkey virus, the p
rototype type D retrovirus, has been expressed to high levels in bacte
ria under the control of the phage T7 promoter. Electron microscopic s
tudies of induced cells revealed the assembly of capsid-like structure
s within inclusion bodies that formed at the poles of the cells 6 h af
ter induction with isopropyl-beta-D-thiogalactopyranoside (IPTG). The
inclusion bodies and enclosed capsid-like structures were solubilized
completely in 8 M urea, but following renaturation, we observed assemb
ly in vitro of capsid-like structures that demonstrated apparent icosa
hedral symmetry. These results demonstrate for the first time that ret
roviral capsid precursors have the propensity to self-assemble in vitr
o and point to new approaches for the analysis of retroviral assembly
and structure.