cobA, a red fluorescent transcriptional reporter for Escherichia coli, yeast, and mammalian cells

We demonstrate the use of Propionibacterium freudenreichii uroporphyrinogen III methyltransferase (cobA) as a reporter of gene expression in Escherich ia coli, fission yeast, and mammalian cells. Overexpression of cobA in cell s resulted in bright red fluorescence that was visualized with standard flu orescence microscopy and fluorescence-activated cell sorting analysis at th e single-cell level. As with green fluorescent protein (GFP), no addition o f exogenous substrate was required. When expressed in Chinese hamster ovary cells from a bicistronic transcript cobA and GFP gave rise to fluorescence signals of similar intensity. The bright red fluorescence generated by the cobA reporter promises a better signal-to-noise ratio than blue and green fluorescent reporter systems, as autofluorescence and light scattering of c ells, media, and materials are reduced in the red wavelengths.