Resolution and identification of iron-containing antigens in membrane vesicles from Escherichia coli

Iron-containing antigens present in membrane vesicles prepared from Escherichia coli ML 308-225 were analyzed by crossed immunoelectrophoresis following growth of the organism in the presence of 59Fe. Seven discrete antigens (or antigen complexes) are detected by autoradiography, and six contain primarily nonheme iron. Three immunoprecipitates are positively identified as NADH dehydrogenase (EC 1.6.99.3), NADPH dehydrogenase (EC 1.6.99.1), and glutamate dehydrogenase (EC 1.4.1.4) based on activity stains for these enzymes. Two other immunogens containing nonheme iron correspond to antigens no. 22 and 37 in the crossed immunoelectrophoresis reference pattern of Owen & Kaback [Owen, P., & Kaback, H. R. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 3148]. In addition, the immunoprecipitate corresponding to Braun's lipoprotein contains tightly bound iron.