The erythrocruorin of Eisenia fetida. I. Properties and subunit structure.
The erythrocruorin of Eisenia fetida possesses a relative molecular mass, determined by sedimentation equilibrium, of (3.82 +/- 0.05) . 10(6). According to the iron and heme contents, 0.218 +/- 0.008% and 2.34 +/- 0.02% by mass, respectively, it contains 144 hemes per molecule. The dimensions of the molecule observed by electron microscopy are 25.0 X 16.5 nm (diameter X height). SDS-polyacrylamide gel electrophoresis indicates that the erythrocruorin consists of six subunits (Mr 14,900, 15,300, 17,200, 19,700, 31,600 and 40,000). Oxygen binding studies showed that E. fetida erythrocruorin has a high oxygen affinity (P50 = 2.8 Torr at pH 7.5), exhibits a slight bohr effect and possesses a high cooperativity with the Hill coefficient h = 3.7-4.8. Treatment of the erythrocruorin either by freezing and thawing or by aging or exposure to alkaline pH converts it irreversibly into a state of lower cooperativity with h = 2.0-2.6. A model of the subunit structure of the erythrocruorin is proposed which takes into account the physiochemical and oxygen-binding properties of the erythrocruorin and the subunits obtained upon its dissociation.
D000818:Animals; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004902:Erythrocruorins / Q000032:analysis*; D006418:Heme / Q000032:analysis; D006454:Hemoglobins / Q000032:analysis*; D007501:Iron / Q000032:analysis; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D008970:Molecular Weight; D009835:Oligochaeta / Q000032:analysis*; D010101:Oxygen Consumption; D013053:Spectrophotometry
D004902:Erythrocruorins; D006454:Hemoglobins; D046911:Macromolecular Substances; D006418:Heme; D007501:Iron