Bolling Sullivan

Hemoglobins of two terebellid polychaetes: Enoplobranchus sanguineus and Amphitrite ornata

1. 1. The intracellular, coelomic hemoglobins of the terebellid annelids Enoplobranchus sanguineus and Amphitrite ornata are momoneric proteins possessing high O2 affinities (half-saturation O2 tension, P50 = 1.4 and 2.8 mm, respectively, at 20°C), and lacking homotropic or heterotropic interactions in O2 binding. These O2 affinities are high relative to extracellular vascular hemoglobins, but low relative to mammalian myoglobins, due to considerably higher rates of O2 dissociation. 2. 2. The extracellular, multi-subunit hemoglobin (erythrocruorin) from the vascular system of A. ornata has a low O2 affinity (P50 about 11 mm Hg at 20°C) and shows significant heme-heme interaction (Hills constant n50 = 1.5–2.0). It lacks a Bohr effect between pH 5.8 and 8.0, but shows a large increase in O2 affinity above pH 8.0 that may be due to dissociation into high affinity subunits. 3. 3. The amino acid composition and the amino acid sequence for the first 29 residues of intracellular E. sanguineus hemoglobin show a surprising lack of homology with other simple heme proteins.

Urea Tolerance as a Molecular Adaptation of Elasmobranch Hemoglobins

Urea is maintained at moderately high concentrations in the blood and tissues of marine elasmobranchs. Functional properties of the hemoglobins fromn several elasmobranch species are unaffected by urea concentrations as high as 5 molar. This in. sensitivity to urea, which is not observed with human hemoglobin, is accompanied by an increased sensitivity to sodium chloride.

The role of coelomic and vascular hemoglobin in the annelid family terebellidae

Abstract 1. 1. Monomeric hemoglobins extracted from terebellid coelomic cells have high oxygen affinities (1–3 mm Hg) with no co-operativity or phosphate dependence in oxygen binding. Hill plots describing deoxygenation of hemoglobins within cells have similar P 50 s, but the curves are biphasic. 2. 2. The high molecular weight hemoglobins dissolved in blood have a relatively low oxygen affinity (10 mm Hg) with slight co-operativity and no sensitivity to phosphates and NaCl. In vivo they transport oxygen primarily to coelomic fluid rather than deep tissue. 3. 3. Terebellid hemoglobins are responsible for 30–55 per cent of total oxygen consumption at p O 2 s prevailing both at high tide, when oxygen transport is believed to be their major function, and at low tide when oxygen storage predominates.

Elasmobranch hemoglobins: Dimerization and polymerization in various species

Abstract 1. 1. Electrophoretic studies of hemolysates from fourteen species of elasmobranchs revealed multiple components in all species. Many species showed numerous hemoglobin phenotypes indicative of a high degree of polymorphism. 2. 2. Gel filtration experiments revealed the presence of polymeric hemoglobins in many hemolysates. Oxidation of hemoglobins with ferricyanide promoted the polymerization of hemoglobin tetramers to octamers and larger aggregates. Reduction of polymer with mercaptoethanol dissociated most polymer aggregates. Reaction of available sulfhydryl groups in freshly prepared hemolysates with iodoacetic acid prevented polymerization and showed that most polymer formation occurs in vitro . 3. 3. Hemoglobins from adult spiny dogfish sharks, Squalus acanthias , are dimeric molecules which aggregate to tetramers upon deoxygenation. Hemoglobins from pups behave similarly, but unlike adult hemoglobins they will not form disulfide-bridged polymers. 4. 4.Most globin chains from elasmobranch hemolysates have molecular weights near 16,000. However, a minor component in hemolysates from the bullnose ray, Myliobatis freminvillei , appears to contain a chain with a molecular weight near 26,000.

Oxygenation Properties of Snake Hemoglobin

Natrix taxispilota hemoglobin has a very high oxygen affinity which depends upon pH in an unusual manner. The oxygen affinity increases slightly upon protein dilution, but the pKs of the Bohr groups are unchanged. Oxidation promotes hemoglobin polymerization, which can be inhibited by prior treatment with iodoacetamide. Reaction with iodoacetamide also causes a slight increase in the oxygen affinity, no change in the pKs of the Bohr groups, and a drastic reduction in heme-heme interaction.

Anion modulation of the negative Bohr effect of haemoglobin from a primitive amphibian.

THE Congo eel (Amphiuma means) is a primitive salamander that respires through its lungs, gills and integument. It lives in swamps, ditches and rice fields in the south-eastern USA. When pools and swamps become stagnant and water levels drop, Amphiuma will burrow and hibernate in the mud. In this letter we report that when organic phosphate cofactors are low or absent, as might be true during hibernation, the haemoglobin of this amphibian has unusual properties which may help the animal to extract oxygen from a low pH environment. The molecular adaptation exhibited by Amphiuma haemoglobin is a pH dependence of oxygen binding that is reversed relative to that of most haemoglobins. Low pH brings about a large increase in the oxygen affinity of stripped Amphiuma haemoglobin. This negative Bohr effect indicates that protons are bound as oxygen is bound. This is in contrast to the release of protons that usually accompanies oxygenation. New Bohr groups must be present in this amphibian haemoglobin, or the normal Bohr groups must be drastically modified. From a physiological viewpoint it is of interest that the Bohr effect in vitro is subject to regulation by organic phosphate cofactors.

Hemoglobin polymorphism in fishes. I. Complex phenotypic patterns in the toadfish, Opsanus tau

Hemolysates of erythrocytes from toadfish (Opsanus tau) are complex mixtures containing 13–18 individual hemoglobin components. Polyacrylamide gel electrophoresis shows that hemoglobin is rather evenly distributed among the bands. Seldom does a single component amount to more than 20% of the total hemolysate. An unusually high degree of polymorphism exists in populations of the toadfish. Six major phenotypes occur commonly at Beaufort, North Carolina, and four of the six phenotypes were present in a sample of 11 toadfish from Gloucester Point, Virginia. Six minor phenotypes occur but have not been studied extensively. The genetic explanation of this hemoglobin polymorphism remains obscure.

Hemoglobin of the electric atlantic torpedo, Torpedo nobiliana: A cooperative hemoglobin without bohr effects

Abstract Hemoglobin of Torpedo nobiliana binds oxygen with a low degree of cooperativity, n ⩽ 1.5, but shows no appreciable pH dependence or response to organic phosphates. At neutral pH stripped Torpedo hemoglobin has a low oxygen affinity relative to stripped human hemoglobin with P 50 values of 15.8 mm Hg versus 0.85 mm Hg. The lower affinity of Torpedo hemoglobin can be attributed to slightly lower rates of ligand binding and considerably higher rates of ligand dissociation. Hemolysates of Torpedo hemoglobin show several electrophoretic zones, indicative of multiple hemoglobin components. Molecular weight studies indicate that Torpedo hemoglobin is normally tetrameric, but forms polymers readily under oxidizing conditions. In addition, Torpedo hemoglobin differs from most vertebrate hemoglobins in that NaCl increases its oxygen affinity. The NaCl effect is accompanied by increased rates of ligand binding.

Oxygen equilibria and ligand-binding kinetics of erythrocruorins from two burrowing polychaetes of different modes of life,Marphysa sanguinea andDiopatra cuprea

SummaryOxygen equilibria, ligand-binding kinetics and some other physicochemical properties are reported for erythrocruorins of two intertidal polychaetes:Marphysa sanguinea, which inhabits simple, relatively stagnant burrows, andDiopatra cuprea, which inhabits impermeable, parchment-like tubes that are vigorously ventilated.Marphysa erythrocruorin has a higher O2 affinity, which is less pH dependent (at pH 7.3 and 20°C, half-saturation O2 tension,P50, and Bohr factor, ϕ=ΔlogP50/ΔpH, are 0.8 mm Hg and −0.25, respectively) than the corresponding parameters (P50=5.5; ϕ=−0.86) inDiopatra (Figs. 1 and 2). In contrast to vertebrate haemoglobins, inorganic salts increase erythrocruorin O2 affinity (Fig. 3). The kinetic rates of ligand binding and dissociation ofMarphysa andDiopatra erythrocruorins (Tables 1 and 2) correlate well with the measured O2 affinities and appear to illustrate basic molecular adaptations of the two species to their respective micro-environmental conditions.

THE HAEMOGLOBIN SYSTEMS OF THE BLOODWORMS GLYCERA DIBRANCHIATA AND G. AMERICANA. OXYGEN BINDING PROPERTIES OF HAEMOLYSATES AND COMPONENT HAEMOGLOBINS

Abstract 1. 1. Oxygen equilibria are reported for the haemolysates of Glycera dibranchiata and G. americana and for the polymeric and monomeric fractions and the isolated major electrophoretic components of G. dibranchiata haemoglobin. 2. 2. In contrast to previously published data, no evidence was found for a functionally-significant interaction between the polymeric and monomeric fractions in G. dibranchiata . Two electrophoretic components of the monomer show virtually identical oxygen affinities (P 50 , 5 mm at 20°C) and no cooperativity in oxygen-binding. Four major polymeric components show similar oxygen affinities (P 50 ∼ 10–13 mm, at pH 7.3 and 20°C), pH sensitivities (Δ log P 50 /Δ pH ∼ 0.3) and cooperativity ( n , 1.2–1.6). 3. 3. G. americana haemolysates reveal oxygen affinities and pH and temperature dependency of oxygen-binding similar to those of G. dibranchiata haemolysates, and a molecular weight heterogeneity indicating the presence of a major tetrameric and a minor dimeric/monomeric haemoglobin fraction. 4. 4. The data are discussed in relation to haemoglobin function in bloodworms.