6. PROPERTIES OF FISH HEMOGLOBINS
217
the largest number of components (salmon and trout) are also among
the most metabolically active. In such fish the properties of the hemoglobin are quite critical. The oxygen requirements of a salmon on its
upstream spawning migration would appear to place a considerable
constraint on the variability of the physiological properties of its
hemoglobins. The existence of two different hemoglobins in the
Chum salmon with entirely different oxygen transport properties suggests that one of these pigments may be of physiological significance
under one set of conditions, and the other pigment under a different
set. This would mean that only half the pigment is “adapted at any
one time.
B. Primary Structure
The primary structure of a polypeptide chain is the sequence of
amino acid residues. This sequence is now believed uniquely to determine the three-dimensional folding: the extent of helical arrangement and determination of the spatial distribution of the amino acid
side chains. This distribution determines which residues will be available for the intermolecular interactions responsible for subunit aggregation. Interchain interactions are physiologically important because
they form the basis of the interaction between the oxygen-binding sites
(hemes) and so are responsible for the shape of the oxygen equilibrium
curve. Very little information on these subjects as yet exists for fish
hemoglobins. The fact that many of them have oxygen equilibria
similar to those of mammalian hemoglobins suggests that the interactions between the subunits may be very similar. The amino acid
sequence is known for only two polypeptide chains: the a chain of the
carp (Hike and Braunitzer, 1968) and one component from the lamprey, Lampetra fluuiatilis ( Braunitzer and Fujiki, 1969). Fragmentary data
exist on the amino acid composition, NH,-terminal and COOH-terminal
residues for several other fish hemoglobins.
Zuckerkandl et al. (1960), in a survey of the hemoglobins from a
wide variety of vertebrates, examined the tryptic peptide patterns
from four fish: the sheepshead, Pimelometopon pulcher, the shark,
Cephaloscyllium uter, the South American lungfish, Lepidosiren paradoxa, and the Pacific hagfish, Polistotrema stouti. They found that the
patterns for the four fish differed among themselves much more than
the mammalian patterns and that the shark and sheepshead differed
as much from the lungfish pattern as from the human pattern. They
concluded that no large soluble tryptic peptide appeared to exist which
was unchanged throughout vertebrate evolution.
217
the largest number of components (salmon and trout) are also among
the most metabolically active. In such fish the properties of the hemoglobin are quite critical. The oxygen requirements of a salmon on its
upstream spawning migration would appear to place a considerable
constraint on the variability of the physiological properties of its
hemoglobins. The existence of two different hemoglobins in the
Chum salmon with entirely different oxygen transport properties suggests that one of these pigments may be of physiological significance
under one set of conditions, and the other pigment under a different
set. This would mean that only half the pigment is “adapted at any
one time.
B. Primary Structure
The primary structure of a polypeptide chain is the sequence of
amino acid residues. This sequence is now believed uniquely to determine the three-dimensional folding: the extent of helical arrangement and determination of the spatial distribution of the amino acid
side chains. This distribution determines which residues will be available for the intermolecular interactions responsible for subunit aggregation. Interchain interactions are physiologically important because
they form the basis of the interaction between the oxygen-binding sites
(hemes) and so are responsible for the shape of the oxygen equilibrium
curve. Very little information on these subjects as yet exists for fish
hemoglobins. The fact that many of them have oxygen equilibria
similar to those of mammalian hemoglobins suggests that the interactions between the subunits may be very similar. The amino acid
sequence is known for only two polypeptide chains: the a chain of the
carp (Hike and Braunitzer, 1968) and one component from the lamprey, Lampetra fluuiatilis ( Braunitzer and Fujiki, 1969). Fragmentary data
exist on the amino acid composition, NH,-terminal and COOH-terminal
residues for several other fish hemoglobins.
Zuckerkandl et al. (1960), in a survey of the hemoglobins from a
wide variety of vertebrates, examined the tryptic peptide patterns
from four fish: the sheepshead, Pimelometopon pulcher, the shark,
Cephaloscyllium uter, the South American lungfish, Lepidosiren paradoxa, and the Pacific hagfish, Polistotrema stouti. They found that the
patterns for the four fish differed among themselves much more than
the mammalian patterns and that the shark and sheepshead differed
as much from the lungfish pattern as from the human pattern. They
concluded that no large soluble tryptic peptide appeared to exist which
was unchanged throughout vertebrate evolution.