An improved GFP cloning cassette designed for prokaryotic transcriptional fusions.

A new gfp cloning cassette designed for prokaryotic transcriptional fusions has been constructed. This cassette consists of gfp (containing the S65T 'red-shift' [Heim et al. (1995) Nature 373, 663-664] and F64L 'protein solubility' [Cormack et al. (1996) Gene 173, 33-38] mutations) flanked by convenient restriction sites, a translational enhancer, and a consensus ribosome binding site with an optimized spacer region. gfp fusion strains containing this cassette demonstrate from 40- to 80-fold greater fluorescence intensity than wild-type gfp fusion strains. Additionally, this cassette confers sufficient fluorescence to recipient cells to be used in low copy-number plasmids, with promoters conferring low levels of transcription, and in bacterial taxa other than Escherichia, such as Pseudomonas.