Recombinant Geochelone nigra Hemoglobin subunit alpha-D (HBAD)
Description
2.1. Sequence and Expression
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HBAA is a full-length protein (142 amino acids) expressed in E. coli or yeast systems, with >85% purity confirmed via SDS-PAGE .
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While HBAD’s sequence is not documented, tortoise hemoglobin subunits typically exhibit conserved globin folds but with species-specific amino acid substitutions .
2.2. Oxygen Transport Role
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Hemoglobin alpha subunits (including HBAA) form heterotetramers with beta subunits to bind and release oxygen . HBAD would likely fulfill an analogous role, albeit with potential differences in oxygen affinity due to sequence divergence.
2.3. Biochemical Properties
| Property | HBAA ( Reference ) | Inferred HBAD |
|---|---|---|
| Molecular Weight | ~16 kDa | ~16 kDa |
| Expression Host | E. coli/yeast | Likely E. coli |
| Purity | >85% (SDS-PAGE) | Expected >85% |
| Storage | -20°C/-80°C | -20°C/-80°C |
3.1. Biomedical Research
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HBAA is used in studies of oxygen delivery mechanisms and hemoglobinopathies . HBAD could similarly serve as a model for evolutionary adaptation of oxygen transport proteins in reptiles .
3.2. Protein Engineering
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Recombinant tortoise hemoglobin subunits (e.g., HBAA) are often studied for their stability and resistance to oxidative stress . HBAD may offer unique structural features for biotechnological applications, such as drug delivery systems .
Limitations and Gaps in Data
Product Specs
Target Background
Q&A
Basic Research Questions
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What is the genomic structure of Hemoglobin subunit alpha-D (HBAD) in Geochelone nigra?
The hemoglobin alpha-D chain in Geochelone nigra (Galápagos giant tortoise) is part of the alpha-globin gene family. While the specific genomic structure in G. nigra has not been fully characterized in the provided research, studies of related species such as Geochelone carbonaria show that the alpha-D cDNA is 539 bp with an ATG start codon at position 46, TGA stop codon at position 469, and AATAAA polyadenylation signal at position 520 . The gene typically encodes 141 amino acid residues, consistent with other chelonian alpha-D chains . The genetic organization likely resembles the alpha-globin gene cluster structure seen in other vertebrates, with multiple loci arranged in a specific order, though the exact arrangement in G. nigra would require specific genomic analysis.
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How does the HBAD amino acid sequence in Geochelone nigra compare with other turtle species?
Comparative analysis of alpha-D chains across chelonian species reveals high sequence conservation with specific variations. In closely related species, G. carbonaria and G. denticulata, the alpha-D chains differ by only four amino acid residues while both maintaining 141 total residues . When comparing these turtle hemoglobin alpha-D chains with human hemoglobin alpha-chains, notable alterations can be observed in functionally important regions, including: α110 Ala→Gly, α114 Pro→Gly, α117 Phe→Tyr, and α122 His→Gln . Sequence homology analysis demonstrates that turtle alpha-D chains share greater similarity with avian alpha-D chains than with snake, lizard, frog, or fish alpha-chains, supporting the evolutionary relationship between chelonians and birds .
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What evolutionary insights does HBAD provide regarding the phylogenetic position of Geochelone nigra?
Phylogenetic analysis of alpha-D chains provides valuable insights into chelonian evolution. Research demonstrates that alpha-D chains from turtles like Geochelone species show closer evolutionary relationships to those of birds than to those of snakes and lizards . This finding supports broader phylogenomic evidence positioning turtles closer to archosaurs (birds and crocodilians) than to lepidosaurs (snakes and lizards) in the amniote phylogenetic tree. The high sequence conservation between Geochelone species (with only four amino acid differences between G. carbonaria and G. denticulata) indicates recent divergence within this genus . Additionally, population genomic studies of G. nigra across the Galápagos archipelago can provide insights into island speciation and adaptive radiation of these iconic tortoises .
