A HISTIDINE BINDING-PROTEIN OF ESCHERICHIA-COLI - A COMPONENT OF CYSTINE BINDING-PROTEIN OF ESCHERICHIA-COLI

Commercially obtained cystine binding protein (CBP), an osmotic shock protein of Escherichia coli, was studied in an effort to determine its binding characteristics. Sodium dodecyl sulfate polyacrylamide gel el ectrophoresis (SDS/PAGE) analysis of commercially obtained CBP showed three protein bands. N-terminal amino acid microsequencing and subsequ ent computer search revealed that the sequence of one of these protein s (25-kDa) was nearly identical to histidine binding protein (HisJ) of Salmonella typhimurium. Purification of CBP by HPLC yielded four prot ein peaks, of which one bound histidine exclusively. Binding was maxim al at pH 5.0 to 6.0, at 4-degrees-C, did not require calcium or magnes ium ions and was not inhibited by reduction of CBP disulfide bonds. Am ino acids other than histidine or cystine did not bind to CBP. These d ata show that commercially available CBP is not a homogenous protein; it contains a histidine as well as a cystine binding component.