Purification and Properties of a Sulfate-binding Protein from Salmonella typhimurium

Sulfate is bound firmly to Salmonella typhimurium. The binding ability is repressible. The binding site is located near the cell surface, and has been suggested as playing a role in active transport of sulfate. A simple procedure for obtaining the sulfate-binding material in homogeneous form is reported here. The material has a molecular weight of 32,000 and is of typical amino acid composition, except that it lacks the sulfur-containing amino acids. No cofactor or energy requirements were found. One sulfate ion is bound per molecule at saturation. The dissociation constant is low (as low as 0.02 µm), and is highly dependent on ionic strength.