A Biophysical and Biochemical Study of the Erythrocruorin of Maoridrilus Montanus

Abstract

The biophysical and biochemical properties of the erythrocruorin from the New Zealand native earthworm Maoridrilus montanus have been studied. In gel filtration four components A, B, C and D representing 2%, 5%, 90% and 3% respectively of the total material at pH 7.0 are evident. (i) Fraction C This component has a molecular weight of 3.2 x 10 6 dalton at pH 7.0 by gel filtration. Under the electron microscope it appears to be composed of 12 subunits arranged in 2 superimposed hexagonal rings. The absorption spectrum and N-terminal groups are reported. The haem and iron contents of the molecules are 2.78% and 0.219% respectively. Gel filtration at pH 9.0 shows that the molecule dissociates into subunits with molecular weights of 230,000 and 130,000 for peaks c and d, and 1.9 x 10 6 and 1.1 x 10 6 daltons for peaks a and b respectively. Gel filtration at pH 11 shows that the molecule dissociates into subunits with Mr of 160,000, 100,000 and 45,000 corresponding to peaks A, B and C respectively. In the presence of SDS-2-mercaptoethanol the protein dissociates into 9 bands with Mr ranging from 12,380 → 100,000. In the presence of SDS only 5 subunits are observed ranging from Mr of 13,180 → 81,200. Alkaline electrophoresis experiments were also carried out on the protein revealing 2 subunits at pH 9 and 1 subunit after dissociation at pH 11.