The oxygen-binding properties of hemocyanin from the mollusk Concholepas concholepas
| Autor: | María Inés Becker, Andrea González, Alfredo E. De Ioannes, Esteban Nova, Augusto Manubens, Miguel Del Campo, Jorge Ferreira |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
0301 basic medicine
endocrine system medicine.medical_treatment Biophysics chemical and pharmacologic phenomena Cooperativity Biochemistry Analytical Chemistry 03 medical and health sciences 0302 clinical medicine Protein Domains medicine Cytochrome c oxidase Animals Concholepas concholepas Submitochondrial particle Molecular Biology biology Chemistry Hemocyanin Hydrogen-Ion Concentration biology.organism_classification Concholepas Oxygen Protein Subunits 030104 developmental biology Mollusca 030220 oncology & carcinogenesis Hemocyanins biology.protein Oxygen binding Keyhole limpet hemocyanin |
| Zdroj: | Biochimica et biophysica acta. Proteins and proteomics. 1865(12) |
| ISSN: | 1570-9639 |
| Popis: | Hemocyanins have highly conserved copper-containing active sites that bind oxygen. However, structural differences among the hemocyanins of various mollusks may affect their physicochemical properties. Here, we studied the oxygen-binding cooperativity and affinity of Concholepas concholepas hemocyanin (CCH) and its two isolated subunits over a wide range of temperatures and pH values. Considering the differences in the quaternary structures of CCH and keyhole limpet hemocyanin (KLH), we hypothesized that the heterodidecameric CCH has different oxygen-binding parameters than the homodidecameric KLH. A novel modification of the polarographic method was applied in which rat liver submitochondrial particles containing cytochrome c oxidase were introduced to totally deplete oxygen of the test solution using ascorbate as the electron donor. This method was both sensitive and reproducible. The results showed that CCH, like other hemocyanins, exhibits cooperativity, showing an inverse relationship between the oxygen-binding parameters and temperature. According to their Hill coefficients, KLH has greater cooperativity than CCH at physiological pH; however, CCH is less sensitive to pH changes than KLH. Appreciable differences in binding behavior were found between the CCH subunits: the cooperativity of CCH-A was not only almost double that of CCH-B, but it was also slightly superior to that of CCH, thus suggesting that the oxygen-binding domains of the CCH subunits are different in their primary structure. Collectively, these data suggest that CCH-A is the main oxygen-binding domain in CCH; CCH-B may play a more structural role, perhaps utilizing its surprising predisposition to form tubular polymers, unlike CCH-A, as demonstrated here using electron microscopy. |
| Databáze: | OpenAIRE |
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