TY - JOUR
T1 - Subunit structure of earthworm erythrocruorin
AU - David, Melvyn M.
AU - Daniel, Ezra
PY - 1974/7/25
Y1 - 1974/7/25
N2 - The subunit structure of earthworm erythrocruorin was studied. The native protein was found to have a sedimentation coefficient of 61.1 S and a molecular weight, as determined by sedimentation equilibrium, of 3.84 × 106. Dissociation of the 60 S molecule was observed at acid and basic pH. Calcium ion was found to prevent dissociation in the basic range. Dissociated species of 10.1, 3.5 and 2.3 S were isolated and their molecular weights determined to be 163 × 103, 41 × 103 and 22 × 103, respectively. On a molecular weight basis, the native molecule consists of twenty-four 10 S subunits, each of which is composed of four 3.5 S units, which are further divided into two 2.3 S units. The 2.3 S species contains a single heme per molecule. A model of the 60 S molecule, where the twenty-four 10 S subunits are arranged into four concentric layers of six subunits each, is proposed. Support for this arrangement is provided by the excellent agreement between the sedimentation coefficient of a 1 24th unit calculated by the application of Kirkwood's (1954) theory with the experimentally determined sedimentation coefficient of the 10 S subunit. An 88 S aggregate observed at the transition pH of acid dissociation is attributed to a side-by-side association dimer of the 60 S molecule.
AB - The subunit structure of earthworm erythrocruorin was studied. The native protein was found to have a sedimentation coefficient of 61.1 S and a molecular weight, as determined by sedimentation equilibrium, of 3.84 × 106. Dissociation of the 60 S molecule was observed at acid and basic pH. Calcium ion was found to prevent dissociation in the basic range. Dissociated species of 10.1, 3.5 and 2.3 S were isolated and their molecular weights determined to be 163 × 103, 41 × 103 and 22 × 103, respectively. On a molecular weight basis, the native molecule consists of twenty-four 10 S subunits, each of which is composed of four 3.5 S units, which are further divided into two 2.3 S units. The 2.3 S species contains a single heme per molecule. A model of the 60 S molecule, where the twenty-four 10 S subunits are arranged into four concentric layers of six subunits each, is proposed. Support for this arrangement is provided by the excellent agreement between the sedimentation coefficient of a 1 24th unit calculated by the application of Kirkwood's (1954) theory with the experimentally determined sedimentation coefficient of the 10 S subunit. An 88 S aggregate observed at the transition pH of acid dissociation is attributed to a side-by-side association dimer of the 60 S molecule.
UR - http://www.scopus.com/inward/record.url?scp=0016188055&partnerID=8YFLogxK
U2 - 10.1016/0022-2836(74)90561-0
DO - 10.1016/0022-2836(74)90561-0
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AN - SCOPUS:0016188055
SN - 0022-2836
VL - 87
SP - 89-98,IN15-IN17,99-101
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 1
ER -