Summary:

1. The top blast hit of b2422 is AF1608 which plays the role as ATPase in spermidine/putrescine ABC transporters system. The AF1608 is paralogous with AF0092.

2. AF0094 is hypothetical protein (lipoprotein ?) which might play a role in this transporter system.

3. b3917 is paralogous with b2425 due to from the gene duplication. And they share the same membrane protein and ATP-binding protein.

In Escherichia coli, sulfate and thiosulfate ions are transported by an ABC-type transporter consisting of both the membrane components (the products of cysT, cysW, and cysA genes) and the periplasmic binders (the products of cysP and sbp genes). The single cysP and sbp mutants are able to utilize both sulfate and thiosulfate as a sole sulfur source, while the inactivation of both genes leads to cysteine auxotrophy resulting from the block in the transport of both ions. (Bacteriol 1995 Jul;177(14):4134-6 Sulfate and thiosulfate transport in Escherichia coli K-12: evidence for a functional overlapping of sulfate- and thiosulfate-binding proteins. Sirko A, Zatyka M, Sadowy E, Hulanicka D PMID: 7608089, UI: 95332222).

The cysPTWA operons of Escherichia coli encode components of periplasmic transport systems for sulfate and thiosulfate and are regulated as part of the cysteine regulons. In vitro transcription initiation from the cysP promoter was shown to require both CysB protein and either O-acetyl-L-serine or N-acetyl-L-serine, which act as inducers, and was inhibited by the anti-inducer sulfide. Thiosulfate was found to be even more potent than sulfide as an anti-inducer. DNase I protection experiments showed two discrete binding sites for CysB protein in the presence of N-acetyl-L-serine. CBS-P1 is located between positions -85 and -41 relative to the major transcription start site, and CBS-P2 is located between positions -19 and +25. Without N-acetyl-L-serine, the CysB protein protected the region between positions -63 and -11, which was designated CBS-P3. In gel mobility shift assays, the mobility of CysB protein-cysP promoter complexes was increased by O-acetyl-L-serine, N-Acetyl-L-serine had no effect in gel shift experiments, presumably because its anionic charge results in its rapid removal from the complex during electrophoresis. Comparison of DNA fragments differing with respect to binding site position indicated that complexes with CysB protein contain DNA that is bent somewhere between CBS-P1 and CBS-P2 and that O-acetyl-L-serine decreases DNA bending. Binding studies with fragments containing either CBS-P2 alone, CBS-P1 alone, or the entire cysP promoter region suggest a model in which the complex of bent DNA observed in the absence of O-acetyl-L-serine contains a single CysB protein molecule bound to CBS-P3. At relatively low CysB protein concentrations, O-acetyl-L-serine would cause a single CysB protein molecule to bind tightly to CBS-P1, rather than to CBS-P3, thereby decreasing DNA bending and increasing complex electrophoretic mobility. At higher CysB protein concentrations, O-acetyl-L-serine would cause a second molecule to bind at CBS-P2, giving a more slowly migrating complex. (J Bacteriol 1991 Sep;173(18):5876-86 Hryniewicz MM, Kredich NM PMID: 1909324, UI: 91358382).