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Abstract Cytochrome b562 (Escherichia coli) was obtained from E. coli B cells by sonic oscillation of the cell paste or by extraction of acetone-dried cell powders. The purification of cytochrome b562 was carried out with calcium phosphate gel-cellulose and diethylaminoethyl cellulose column chromatography. Crystallization of the hemoprotein was accomplished in 70 to 80% saturated ammonium sulfate. The oxidized form of cytochrome b562 crystallizes as needles. The reduced form crystallizes in a hexagonal form. The heme prosthetic group of cytochrome b562 is iron-protoporphyrin IX. Cytochrome b562 has absorption bands at 562, 531.5, 427, and 324 mµ in the reduced form and 418 and 363 mµ in the oxidized form. Only a weak shoulder was observed in the 280 mµ region. The ratio of ϵ562 (reduced): ϵ280 (oxidized) is 1.5. The α-band shifts from 562 to 558 mµ at liquid nitrogen temperature and does not split. The apoprotein has an absorption peak at 277 mµ and combines with protohemin to reconstitute the original cytochrome. The oxidation-reduction potential (E'0) of cytochrome b562 is 113 mv. The sedimentation constant (s20,w) of cytochrome b562 is 1.64 S. The diffusion coefficient (D) of cytochrome b562 is 11.9 x 10-7 cm2 sec-1. The minimal molecular weight of cytochrome b562 based on an analysis of the ratio of heme to dry weight is 12,000. The molecular weight of cytochrome b562 based on hydrodynamic measurements is 11,700 to 12,700. The molecular weight of cytochrome b562 based on the summation of heme plus amino acid residues is 11,954. The amino acid composition of cytochrome b562 is Lys11, His2, Arg4, Asp16, Thr6, Ser3, Glu14, Pro5, Gly4, Ala15, Val5, Met2, Ile3, Leu9, Tyr2, Phe2, and ammonia11. Cytochrome b562 does not contain cysteine, cystine, or tryptophan residues.
Itagaki et al. (Mon,) studied this question.