A phylogenetic and structural analysis of truncated hemoglobins

Truncated hemoglobins (trHbs) are heme proteins found in bacteria, plants, and unicellular eukaryotes. They are distantly related to vertebrate hemoglobins and are typically shorter than these by 20-40 residues. The multiple amino acid deletions, insertions, and replacements result in distinctive al...

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Bibliographic Details
Published in:Journal of molecular evolution 2006-02, Vol.62 (2), p.196-210
Main Authors: Vuletich, David A, Lecomte, Juliette T J
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Amino acids
Animals
Bacteria
Chemical properties
Conserved Sequence
Evolution, Molecular
Gene Transfer, Horizontal
Hemoglobins - genetics
Ligands
Models, Genetic
Molecular Sequence Data
Phylogeny
Protein Structure, Quaternary
Sequence Homology, Amino Acid
Structural analysis
Truncated Hemoglobins
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Summary:Truncated hemoglobins (trHbs) are heme proteins found in bacteria, plants, and unicellular eukaryotes. They are distantly related to vertebrate hemoglobins and are typically shorter than these by 20-40 residues. The multiple amino acid deletions, insertions, and replacements result in distinctive alterations of the canonical globin fold and a wide range of chemical properties. An early phylogenetic analysis categorized trHbs into three groups, I (trHbN), II (trHbO), and III (trHbP). Here, we revisit this analysis with 111 trHbs. We find that trHbs are orthologous within each group and paralogous across the groups. Group I globins form the most disparate set and separate into two divergent subgroups. Group II is comparatively homogeneous, whereas Group III displays the highest level of overall conservation. In Group I and Group II globins, for which some ligand binding and structural data are available, an improved description of probable protein-ligand interactions is achieved. Other conservation trends are either confirmed (essential glycines in loops), refined (lining of ligand access tunnel), or newly identified (helix start signal). The Group III globins, so far uncharacterized, exhibit recognizable heme cavity residues while lacking some of the residues thought to be important to the trHb fold. An analysis of the phylogenetic trees of each group provides a plausible scenario for the emergence of trHbs, by which the Group II trHb gene was the original gene, and the Group I trHb and Group III trHb genes were obtained via duplication and transfer events.
ISSN:0022-2844
1432-1432
DOI:10.1007/s00239-005-0077-4