A ColE1-compatible vector was constructed to expressed His-tagged fusion pr
otein in Escherichia coli cells. The vector designated pYH31 is derived fro
m pREP4 and pQE31. It was designed to express simultaneously in the same ce
ll, a His-tagged fused protein and a non His-tagged protein from separate p
lasmids. The vector was used to express both subunits of the biphenyl dioxy
genase oxygenase component together in the same E. coli clone.