IDENTIFICATION OF SULFATE STARVATION-REGULATED GENES IN ESCHERICHIA-COLI - A GENE-CLUSTER INVOLVED IN THE UTILIZATION OF TAURINE AS A SULFUR SOURCE

Genes whose expression is regulated by sulfate starvation in Escherich ia coli were identified by generating random translational lacZ fusion s in the chromosome with the lambda placMu9 system, Nine lacZ fusion s trains which expressed beta-galactosidase after growth under sulfate s tarvation conditions but not after growth in the presence of sulfate w ere found, These included two strains with insertions in the dmsA and rhsD genes, respectively, and seven strains in which the insertions we re located within a 1.8-kb region downstream of hemB at 8.5 minutes on the E. coli chromosome, Analysis of the nucleotide sequence of this r egion indicated the presence of four open reading frames designated ta uABCD, Disruption of these genes resulted in the loss of the ability t o utilize taurine (2-aminoethanesulfonate) as a source of sulfur but d id not affect the utilization of a range of other aliphatic sulfonates as sulfur sources. The TauA protein contained a putative signal pepti de for transport into the periplasm; the TauB and TauC proteins showed sequence similarity to STP-binding proteins and membrane proteins, re spectively, of ABC-type transport systems and the TauB protein was rel ated in sequence to a dichlorophenoxyacetic acid dioxygenase, We there fore suggest that the proteins encoded by tauABC constitute an uptake system for taurine and that the product of tauD is involved in the oxy genolytic release of sulfite from taurine, The transcription initiatio n site was deterred 26 to 27 hp upstream of the translational start si te of tauA. Expression of the tauD gene was dependent on CysB, the tra nscriptional activator of the cysteine regulon.