thiBPQ encodes an ABC transporter required for transport of thiamine and thiamine pyrophosphate in Salmonella typhimurium

In Salmonella typhimurium, thiamine pyrophosphate (TPP) is a required cofactor for several enzymes in central metabolism. Herein we identify a new thi operon, thiBPQ (designated sfuABC in Escherichia coli), required for the transport of thiamine and TPP into the cell, Insertions in the operon result in strains that are phenotypically and biochemically defective in thiamine and TPP transport, Data presented herein show that this operon is transcriptionally repressed in the presence of exogenous thiamine, with TPP the likely regulatory molecule. This work represents the first identification of thiamine transport genes in bacteria and demonstrates the function of a proposed ABC transporter in E, coli.