IDENTIFICATION OF A NOVEL SUGAR-H-FUCOSE INTO ESCHERICHIA-COLI( SYMPORT PROTEIN, FUCP, FOR TRANSPORT OF L)

L-Fucose (6-deoxy-L-galactose) is used as sole carbon source by many m icroorganisms, and its transport into Escherichia cell is mediated by an L-fucose-H+ symport activity. In order to determine the nature of a putative transporter encoded by the E. coli fucP gene and identify it s protein product it was cloned downstream of the inducible T7 RNA pol ymerase and lambda OLPL promoters. Induction of the T7 promoter result ed in the expression of [C-14]-L-fucose uptake activity and the concom itant expression of a [S-35]-Met-labelled 32 kDa protein at levels too low for detection by staining with Coomassie brilliant blue or for pr otein sequencing. Induction of the lambda OLPL promoter caused the app earance of L-fucose-H+ symport activity and of a Coomassie brilliant b lue-stained 32 kDa membrane protein expressed at high levels sufficien t for Identification as FucP by N-terminal protein sequencing. The Fuc P protein is, therefore, a sugar-H+ symporter different in amino acid sequence from any other known transporter. These and other results ill ustrate the general unpredictability of cloning strategies for attempt ing the amplified expression of membrane transport proteins.