Bacteriophage Q replicase contains the protein biosynthesis elongation factors EF Tu and EF Ts.

The enzyme, Qbeta replicase, responsible for the replication of the RNA of Escherichia coli pahge Qbeta, is composed of four nonidentical subunits, three of which, I, III, and IV, are coded for by the bacterial genome, while subunit II is phage-specific. SUBUNIT IV IS SHOWN TO BE IDENTICAL TO THE PROTEIN SYNTHESIS ELONGATION FACTOR EF TS BY THE FOLLOWING CRITERIA: coelectrophoresis on polyacrylamide gels in sodium dodecyl sulfate and in urea buffers, identity of the first seven amino acids at the amino-terminus, precipitation of sub-unit IV by anti-EF T-factor serum, and stimulation of EF Tu-GDP exchange by subunit IV. Subunit III is shown to be identical to the protein synthesis elongation factor EF Tu by the following criteria: coelectrophoresis on sodium dodecyl sulfate gels, precipitation of EF Tu by anti-Qbeta replicase serum, binding of guanine nucleotides, and binding of phenylalanyl-tRNA. In addition, Qbeta replicase activity can be reconstituted from subunits I and II with EF Tu and EF Ts.