Structural Biochemistry/Protein function/Heme group/Other Globins
Introduction The globins are a related family of proteins, all of which have similar primary and tertiary structure (amino acid sequence and folding). These proteins all incorporate the globin fold. The haploid human genome contains 1 globin gene for myglobin, two genes for alpha hemoglobin, and one gene for beta hemoglobin, as well as fetal hemoglobin. Recent examination of the human genome has revealed two additional globins.
Neuroglobin is expressed primarily in the brain and at especially high levels in the tetina. Neuroglobin is a monomer that reversibly binds oxygen with an affinity higher than that of hemoglobin. It also increases oxygen availability to brain tissue and provides protection under hypoxic or ischemic conditions, potentially limiting brain damage. It is of ancient evolutionary origin, and is homologous to nerve globins of invertebrates.
Cytoglobin is a globin molecule located in the brain and most notably utilized in marine mammals. It is thought to be a method of protection under conditions of hypoxia. The predicted function of cytoglobin is the transfer of oxygen from arterial blood to the brain.
Berg, Jeremy M. John L. Tymoczko. Lubert Stryer. Biochemistry Sixth Edition. W.H. Freeman and Company. New York, 2007.