The gluconate high affinity transport of GntI in Escherichia coli involves a multicomponent complex system

Within the main system for gluconate utilization in E. coli, the gntT gene (located at the minute 76.4) that encodes a permease, is currently the only element involved in the high affinity transport. In this paper, the nucleotide sequence of the upstream region of this locus was determined. Two open reading frames of 729 bp (gntX) and 573 bp (gntY) were identified as additional gnt genes by complementation studies. Our observations suggest that these loci might conform an operon distinct of gntT under the control of the gntR gene product. Such operon encodes a gluconate periplasmic binding protein (GntX) and a putative membrane-bound protein (GntY). These products and the permease encoded by the gntT gene seem to conform a high-affinity complex transport system for gluconate. We suggest that this novel system could belong to the TRAP transporters.