THE GNTP GENE OF ESCHERICHIA-COLI INVOLVED IN GLUCONATE UPTAKE

The gntP gene, located between the fim and uxu loci in Escherichia col i K-12, has been cloned and characterized. Nucleotide sequencing of a region encompassing the gntP gene revealed an open reading frame of 44 7 codons with significant homology to the Bacillus subtilis gluconate permease, Northern (RNA) blotting indicated that the gntP gene was mon ocistronic and was transcribed as an mRNA with an apparent molecular s ize of 1.54 kb. The transcriptional start point was determined by prim er extension analysis, The gntP gene was found to be under catabolite repression and was not induced by gluconate. Also, expression seemed t o be stringently controlled. Several observations indicated that the G ntP protein is an inner membrane protein; it contains characteristic m embrane-spanning regions and was isolated predominantly from the inner -membrane fraction of fractionated host cells, A topology analysis pre dicted a protein with 14 membrane-spanning segments, The inability of a mutant strain to grow on gluconate minimal medium could be relieved by introduction of a plasmid encoding the gntP gene. Finally, the kine tics of GntP-mediated gluconate uptake were investigated, indicating a n apparent K-m for gluconate of 25 mu M.