Functional consequences of ligand-linked dissociation in hemoglobin from the sea cucumber Molpadia arenicola
| Autor: | Celia Bonaventura, Barrie Kitto, Eraldo Antonini, Maurizio Brunori, Joseph Bonaventura |
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| Rok vydání: | 1976 |
| Předmět: |
Macromolecular Substances
Kinetics Biophysics chemistry.chemical_element Cooperativity Ligands Biochemistry Oxygen chemistry.chemical_compound Hemoglobins Animals Tyrosine Molecular Biology Histidine Carbon Monoxide Binding Sites Ligand (biochemistry) chemistry Spectrophotometry Hemoglobin Carbon monoxide Echinodermata Protein Binding |
| Zdroj: | Biochimica et biophysica acta. 428(3) |
| ISSN: | 0006-3002 |
| Popis: | It has been established that Molpadia hemoglobin tends to dissociate into subunits as oxygen is bound. The kinetics and equilibria of carbon monoxide and ethylisocyanide binding reported here show a dependence on protein concentration that supports the conclusion that the aggregated hemoglobin has a lower ligand affinity than the dissociated subunits. This is true for the isolated D-chain as well as for the unfractionated hemolysate that contains four distinct polypeptide chains (A-D). This indicates that even homopolymers of Molpadia hemoglobin have lower ligand affinity than the dissociated subunits. At high protein concentration hemolysates of Molpadia hemoglobin show slight cooperativity. The time course of ligand binding to the deoxy D-chain also suggests cooperative interactions. The low affinity of the aggregated state may have a different molecular explanation than in human hemoglobin where tetramers of identical subunits (as in Hb H) show high oxygen affinity. The absence of tyrosine and histidine at the C-terminal of the Molpadia D-chains also suggests a different stabilization of the low affinity deoxy state. An additional functional difference between Molpadia hemoglobin and human hemoglobin is that organic phosphates do not alter the ligand affinity of the sea cucumber hemoglobin. |
| Databáze: | OpenAIRE |
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