PHYSICOCHEMICAL CHARACTERISTICS AND OXYGEN-BINDING PROPERTIES OF MULTIPLE HEMOGLOBINS OF WEST-AFRICAN BLOOD CLAM ANADARA-SENILIS (L)

1. 1. Anadara senilis contains two multisubunit haemoglobins, HbI and HbII, which can be separated by gel filtration and electrophoresis. 2. 2. Molecular weight estimates by gel filtration were 24,000-28,500 for HbI, and 54,500-55,500 for HbII. Both haemoglobins had subunit molecular weights of 12,000-14,000 by SDS electrophoresis. 3. 3. Isoelectric focussing resolved HbII into two major components with isoelectric points between pH 5.0 and 6.0 and several minor components; HbI gave a single band at about pH 9.0. 4. 4. The amino acid composition showed that HbI contains more aspartic acid and histidine and much less lysine than HbII. 5. 5. It is concluded that HbI is a dimer and HbII is a tetramer and that the two haemoglobins are constructed from different monomers. 6. 6. The dimer HbI had a higher oxygen affinity (p50, 4.2-6.7 mm Hg) than the tetramer HbII (p50, 8.0-13.0 mm Hg) between pH 6.5 and 7.5. Both haemoglobins bound oxygen co-operatively and both showed a small Bohr effect. © 1978.