A new vector-host system for construction of lacZ transcriptional fusions where only low-level gene expression is desirable

Abstract

We improved a multicopy vector, pRS415 [Simons et al., Gene 53 (1987) 85-96], for use in operon fusion constructions by introducing a new multiple cloning site (MCS) containing eight unique restriction sites upstream from the promoterless reporter gene lacZ. In order to reduce plasmid copy number, a new Escherichia coli strain SP2 (pcnB, delta lac, recA) was constructed. This strain permits analysis of fusions in cases where high gene dosage may be detrimental.