Nucleotide sequence of the phoS gene, the structural gene for the phosphate-binding protein of Escherichia coli

Abstract

PhoS is the structural gene for the phosphate-binding protein, which is localized in periplasm and involved in active transport of phosphate in E. coli. It is also a negative regulatory gene for the pho regulon, and the gene expression is inducible by phosphate starvation. The complete nucleotide sequence of the phoS gene was determined by the method of Maxam and Gilbert. The amino acid sequences at the amino termini of the pre-PhoS and PhoS proteins and at the carboxy terminus of the PhoS protein were determined by using the purified proteins. The amino acid sequence of enzymatically digested peptide fragments of the PhoS protein was determined. The combined data established the nucleotide sequence of the coding region and the amino acid sequence of the pre-PhoS and the PhoS protiens. The pre-PhoS protein contains an extension of peptide composed of 25 amino acid residues at the amino terminus of the PhoS protein, which has the general characteristics of a signal peptide. The mature PhoS protein is composed of 321 amino acid residues, with a MW of 34,422, and lacks the disulfide bond and methionine. The regulatory region of phoS contains a characteristic Shine-Dalgarno sequence at an appropriate position preceding the translational initiation site, 3 possible Pribnow boxes and a -35 sequence. The nucleotide sequence of the regulatory region of phoS was compared with those of phoA and phoE, the genes constituting the pho regulon.