The Hemoglobins of the Bullfrog, Rana catesbeiana

Multiple hemoglobins exist in hemolysates of red cells from both tadpole and adult of the bullfrog, Rana catesbeiana. The proportions and amino acid compositions of the hemoglobin components show considerable variability in hemolysates from different tadpole populations. Amino acid analyses of the polypeptide chains from the major hemoglobin components do not suggest the presence of any chain common to both tadpole and adult bullfrog. Component C (but not B) from the adult polymerizes to form octamers and larger aggregates by disulfide linkage between tetramers. All cysteinyl residues of Component B are reactive to iodoacetamide. Neither reaction with iodoacetamide nor polymerization significantly affect the oxygen equilibrium of frog hemoglobin. Component B has twice the Bohr effect of Component C and a much lower oxygen affinity, particularly at low pH. The oxygen equilibria of mixtures show that Components B and C interact with one another.