Abstract: Three classes of GFP mutants having single excitation maxima around 488 nm are brighter than wild-type GFP following 488 nm excitation. GFPmut1 has a double substitution: F64L, S65T; GFPmut2 has a triple substitution: S65A, V68L, S72A; and GFPmut3 is characterized by the double substitution S65G, S72A. The excitation maxima of the three mutants are at 488 nm, 481 nm and 501 nm respectively. The fluorescence intensities following excitation at 488 nm are an order of magnitude higher than that of wild-type GFP excited at 488 nm in E. coli. The expression of GFP is observable minutes after induction.

Abstract: Regulatory elements (e.g. promoters) activated by a stimulus are isolated by a FACS-based method. Preferably, a library of random fragments representative of a target (e.g. bacterial) genome are cloned in front of a promoterless gfp (green fluorescent protein) sequence in a plasmid, and inserted into target cells. The resulting target cell mixture is sorted according to GFP levels in the presence and the absence of the stimulus. Suitable stimuli include compounds of interest (e.g. drugs), environmental factors (e.g. extracellular acidity), and complex stimuli such as in vivo environments of hosts infected by the target cells. The method allows identifying pathogen genes which are selectively expressed during infection.

Abstract: Three classes of GFP mutants having single excitation maxima around 488 nm are brighter than lid-type GFP following 488 nm excitation. GFPmut1 has a double substitution: F64L, S65T; GFPmut2 has a triple substitution: S65A, V68L, S72A; and GFPmut3 is characterized by the double substitution S65G, S72A. The excitation maxima of the three mutants are at 488 nm, 481 nm and 501 nm respectively. The fluorescence intensities following excitation at 488 nm are an order of magnitude higher than that of wild-type GFP excited at 488 nm in E. coli. The expression of GFP is observable minutes after induction.

Abstract: The invention relates to yeast leukotriene A.sub.4 hydrolase enzymes and nucleic acids.