CIT96μ is a genetically-encoded FRET nanosensor for citrate. It contains amino acids 6-130 of the citA gene from Klebsiella pneumoniae (this includes the citrate binding domain), carrying a K77A amino acid substitution (this reduces the affinity for citrate), flanked by the fluorescent proteins CFP and Venus. Binding of citrate to the citA sequence results in a conformational change which increases FRET efficiency (PMID:22164251).