SummaryThescrgenes located on plasmid pUR400 and responsible for sAucrose (Scr) metabolism ofEscherichia coliK12 and other enteric bacteria have been cloned on a 9.3 kb DNA fragment. The different genes were mapped by transposon insertion mutagenesis, by restriction endonuclease and deletion mapping, and the corresponding gene products were identified. Besides the known structural genesscrA, coding for an EnzymellScr(45 kD) of the phosphoenolypyruvate‐dependent phosphotransferase system (PTS), andscrB, coding for a sucrose 6‐phosphate hydrolase (invertase) (55 kD), two new structural genes were discovered. GenescrKapparently codes for an intracellular and ATP‐dependent fructokinase (39 kD), whilescryseems to code for a sucrose porin (58 kD) in the outer cell membrane. No genes for an Enzyme IIIScrof the PTS or for (a) glycosyltransferase(s) were detected. The four genes form anscroperon (gene order,scrK scrY scrA scrB, transcription from K to B), regulated by a repressor (genescrR, 37 kD) and inducible by sucrose, fructose and fructose‐containing oligosac