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Thermoglobin, oxygen-avid hemoglobin in a bacterial hyperthermophile
J J L Miranda1, David H Maillett, Jayashree Soman
1Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA. jjmirand@fas.harvard.edu
The Journal of Biological Chemistry
|September 2, 2005
Summary
Researchers studied a thermophilic hemoglobin from Aquifex aeolicus, revealing properties potentially shared by ancestral hemoglobins. This offers insights into protein evolution and adaptation to extreme environments.
Area of Science:
- Biochemistry
- Molecular Biology
- Evolutionary Biology
Background:
- Hemoglobin proteins are vital across life, evolving diverse functions from a common ancestor.
- Studying bacterial hyperthermophiles can illuminate ancestral protein traits and adaptation mechanisms.
Purpose of the Study:
- To characterize the hemoglobin from the hyperthermophilic bacterium Aquifex aeolicus.
- To infer potential primordial functions and evolutionary pathways of the hemoglobin superfamily.
Main Methods:
- Identification and cloning of Aquifex aeolicus hemoglobin (AaTgb).
- Recombinant expression, purification, and biochemical characterization of AaTgb.
- Analysis of oxygen-binding properties and stability.
Main Results:
- AaTgb is a monomeric, highly stable protein, resistant to denaturation.
- It exhibits pentacoordinate, ferrous, deoxygenated state and high oxygen avidity (Kd ~1 nM).
- A distal pocket tyrosine forms a hydrogen bond with the bound ligand, contributing to oxygen affinity.
Conclusions:
- The properties of AaTgb suggest it may represent ancestral hemoglobin characteristics.
- These findings provide a basis for understanding hemoglobin evolution and primordial functions.
- The study highlights thermophilic hemoglobins as models for ancient protein structures and functions.