InterPro domain: IPR044203

This entry represents a group of haemoglobin-like proteins found in eubacteria, cyanobacteria, protozoa and plants, but not in animals or yeast [ 1 ]. Truncated hemoglobins (TrHbs) have a truncated 2-over-2 rather than the canonical 3-over-3 alpha-helical sandwich fold [ 2 ]. The variability of the amino acid residues of the heme pocket suggested their partition into three groups that share less than 30% sequence similarity with each other [ 3 ].

This entry includes Glb3, a nuclear-encoded truncated haemoglobin from plants that appears more closely related to HbO than HbN. Glb3 from Arabidopsis thaliana (Mouse-ear cress) exhibits an unusual concentration-independent binding of oxygen and carbon dioxide [ 3 ].

1. Truncated hemoglobins: a new family of hemoglobins widely distributed in bacteria, unicellular eukaryotes, and plants. J. Biol. Chem. 277, 871-4
2. Structural and functional properties of hemoglobins from unicellular organisms as revealed by resonance Raman spectroscopy. J. Inorg. Biochem. 99, 72-96
3. A hemoglobin from plants homologous to truncated hemoglobins of microorganisms. Proc. Natl. Acad. Sci. U.S.A. 98, 10119-24