Direct participation of a host protein in the replication of viral RNA in vitro.

Abstract
A protein with all the properties of the "light" component of QB-replicase can be isolated from uninfected Escherichia coli cells, including strains (e.g., E. coli B) which are not hosts of the QB-virus. "Light" protein from uninfected cells when combined with purified "heavy" protein yields an enzyme capable of producing biologically competent infectious QB-RNA.