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Overproduction of α Chains Provides a Proton-insensitive Component to the Bluefish Hemoglobin System
Expression of α and β chains and their post-translational assembly into α 2 β 2 tetramers is fundamental to the formation and function of most vertebrate hemoglobins. There is a strong evolutionary bias that favors expression of equal amounts of the two types of chains, because cooperativity, pH...
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| Published in: | The Journal of biological chemistry 2005-12, Vol.280 (49), p.40509 |
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| Main Authors: | , , , , |
| Format: | Article |
| Language: | English |
| Online Access: | Get full text |
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| Summary: | Expression of α and β chains and their post-translational assembly into α 2 β 2 tetramers is fundamental to the formation and function of most vertebrate hemoglobins. There is a strong evolutionary bias
that favors expression of equal amounts of the two types of chains, because cooperativity, pH sensitivity, and anionic control
of function occurs only for the α 2 β 2 tetramers. Remarkably, an over-production of α chains, as in the pathological condition known as β thalassemia in humans,
is adaptive rather than pathological in the bluefish hemoglobin system. The thalassemia of the bluefish is a novel means of
providing for oxygen uptake and delivery when low pH conditions incapacitate the highly pH-sensitive Root effect hemoglobins
of the fish. Although fish often have pH-insensitive along with highly pH-sensitive hemoglobins, having pH-insensitive α chain
monomers in circulation is an unusual structural variation. The role of bluefish α chains in oxygen transport is enabled by
their remarkably lower oxygen affinity relative to human α chains. This is the first reported case of a thalassemic condition
that is maintained in a species as an adaptive advantage. |
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| ISSN: | 0021-9258 1083-351X |
| DOI: | 10.1074/jbc.M505353200 |