Isolation of a Second Rifamycin‐Binding from Escherichia coli by Affinity Chromatography

Abstract
When extracts of Escherichia coli are filtered through a Sepharose column containing covalently bound rifamycin a protein is bound which can be eluted either with a high concentration of urea or more specifically with low concentrations of rifamycins. Its Mr is 18000 ± 1000 in the presence of dodecylsulfate, in its absence 36000 ± 3000. The association constant of the protein for rifampicin is 2.4 ± 0.5 × 10−4 M with two binding sites per dimer as determined by equilibrium dialysis. Large amounts of this protein are released from the cells by an osmotic shock.