The nucleotide sequence of Escherichia coli genes for L-fucose dissimilation.

a L-Fucose is dissimilated by Escherichia coli through an inducible pathway mediated by a permease encoded by fucP, an isomerase encoded by fuel, a kinase encoded by fucK, and an aldolase encoded by fucA. The aldolase cleaves fuculose 1-phosphate to dihydroxyacetone phosphate and L-lactaldehyde. Under anaerobic conditions the L-lactaldehyde is reduced to L-l,2-propanediol by an oxidoreductase encoded by fucO. These structural genes, together with the regulatory gene fucR encoding an activator protein, cluster at min 60 of the chromosomal map (1) . Cloning and deletion analysis of the fuc region showed that the structural genes constitute two divergently transcribed operons fucAO , (counterclockwise) and fucPIK (clockwise). The fucR gene is located downstream "* of fucK (2,3) . _. The entire fuc region (8.9 kb) has been sequenced. The sequence of the fucO and fucA genes was presented in a separate paper describing the effects of an insertion (IS5) mutation on the expression of the fucAO and fucPIK operons (3). We report here the sequence from positions 2001 to 8901, which includes the remaining fuc genes. This part of the sequence reveals 6 long open reading frames (ORFs), all of them have good Shine-Dalgarno (SD) ribosome binding sequences which are properly placed. The 4 ORFs assigned to the fucPIK operon and fucR are based on their positions and complementation tests (2). The functions of the 2 other ORFs, if any, are not known. One is located between fucK and fucR encoding a peptide of 134 amino acids. The other is located at the right end of the sequenced region, down stream of fucR, encoding at least 63 amino acids. The region between positions 2075 to 2595 contains controlling elements for the divergently transcribed fucAO and fucPIK operons (3). There are 4 or 5 potential cAMP receptor protein (CRP) binding sites scattered in this region based on homologies to the reported consensus CRP binding sequence (4). Further study is needed to identify the functional sites.