Colicins Ia and Ib have been purified from mitomycin C-induced Escherichia coli strains W 3110 str-r (col Ia) and W3110 str-r (col Ib) by ammonium sulfate precipitation, treatment with diethylaminoethylcellulose, and chromatography on DEAE-Sephadex, phosphocellulose, and hydroxylapatite. Sedimentation velocity and equilibrium centrifugation as well as polyacrylamide gel electrophoresis at several pH values indicated that both colicin preparations were homogeneous. The molecular weight of colicin Ia was determined from its s20,w0 (3.57 S) and D20,w0 (4.12 x 10-7 cm2 sec-1) as well as from sedimentation equilibrium centrifugation and dodecyl sulfate polyacrylamide gel electrophoresis to be approximately 77,600. The molecular weight of colicin Ib was approximately 79,600 (s20,w0 = 3.67 S; D20,w0 = 4.32 x 10-7 cm2 sec-1). Colicins Ia and Ib had f/f0 values of 1.82 and 1.76, respectively.
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Konisky et al. (1970) studied this question.