The hemoglobin system of the brown moray Gymnothorax unicolor

Abstract

The Gymnothorax unicolor hemoglobin system is characterized by two components, called cathodic and anodic on the basis of their isoelectric point, which were separated by ion-exchange chromatography. The oxygen-binding properties of the purified components were studied in the absence and presence of chloride and/or GTP or ATP in the pH range 6.5-8.0. Stripped cathodic hemoglobin showed a small reverse Bohr effect, high oxygen affinity, and low co-operativity; the addition of chloride only caused a small decrease in oxygen affinity. In the presence of GTP or ATP, the oxygen affinity was dramatically reduced, the co-operativity increased, and the reverse Bohr effect abolished. Stripped anodic hemoglobin is characterized by both low oxygen affinity and co-operativity, and displayed a normal Bohr effect; the addition of chloride increased co-operativity, whereas ATP and GTP significantly modulated oxygen affinity at acidic pH values, enhancing the Bohr effect and giving rise to the Root effect. The complete amino-acid sequences of the alpha and beta chains of both hemoglobins were established; the molecular basis of the functional properties of the hemoglobins is discussed in the light of the primary structure and compared with those of other fish hemoglobins.

An Effector of Hemoglobin Structure: The Guanosine 3', 5'-Triphosphate

“…[21][22][23] It seems that GTP can bind and change the secondary and tertiary structures of hemoglobin. We showed that reason of the decreased affinity of hemoglobin for oxygen, as stated by Tamburrini et al, 11 may be because of the changed secondary and tertiary structures of hemoglobin. Our data suggest that GTP acts as a regulator of hemoglobin's affinity for oxygen by structural changes in the protein.…”

“…Tamburrini et al have reported that the affinity of hemoglobin, for oxygen, was reduced dramatically in the present of GTP. 11 However, there are still unanswered questions like: how GTP affects the hemoglobin structure?…”

Hemoglobin function in deep-sea and hydrothermal-vent endemic fish:Symenchelis parasitica(Anguillidae) andThermarces cerberus(Zoarcidae)

“…parasitica typifies class II fish, having cathodic Hb with relatively high O2 affinity, a slight, reversed Bohr effect in the absence of organic phosphate and a large effect of ATP (that normalizes the Bohr effect) as well as an anodic Hb with relatively low affinity and marked Bohr and ATP effects -as found in other anguillids (Weber et al, 1976a;Fago et al, 1995;Tamburrini et al, 2001) and catfish Powers and Edmundson, 1972;Weber et al, 2000;Fig.·8). Unexpectedly, the affinities of stripped S. parasitica Hbs [P50=14·Torr (1.89·kPa) and 33·Torr (4.4·kPa) for Hb I and II, respectively, at pH 7.2 and 25°C] are low compared with those obtained by the same technique in eel and catfish cathodic and anodic Hbs [P50=≈2·Torr (0.23·kPa) and ≈8.5·Torr (1.13·kPa), respectively; Weber et al, 1976a;Fago et al, 1995Fago et al, , 1997bWeber, 2000a] but are similar to those in trout Hbs [P50=~17-20·Torr (2.27-2.67·kPa) at 20°C; Weber et al, 1976b] -all of these species are classified as class II.…”

Phylogenetic relationships of twenty Gymnothorax species based on cytochrome b sequence data

“…In another study, Ling reported a decrease in the Sr/Ca ratios in the otoliths of Gymnothorax reticularis during metamorphosis (Ling et al, 2005). In addition, Tamburrini et al (2001) studied the structure/function relationships of the brown moray (Gymnothorax unicolor) hemoglobin system. However, there is still debate on the number of Gymnothorax species that inhabit the South and East China Seas.…”