Globin, coordination with heme

The rabbit reticulocyte, which synthesizes about 90 of its protein as hemoglobin, offers one of the best examples of translational control of protein synthesis in animal cells. In the complete absence of a nucleus (which is extruded from the cell during its maturation) it coordinates the production of the a and R chains of globin, both with each other and with the supply of heme. However, the exact mechanism of this translational control is not yet fully understood, and only a partial description of what appears to be a surprisingly complex process can be given below. 

Coordination of heme and globin synthesis is the rule during erythropoiesis. While heme is synthesized in mitochondria, protein s)mthesis occurs in the endoplasmic reticulum. Control between compartments may have more far-reaching effects than merely coordinated hemoglobin manufacture. Indeed, there is evidence from studies with deprivation of amino acids, glucose, or oxygen that protein synthesis is coupled in some manner to the metabolic economy. So conceived, the role of hemin in the cytochromes may serve as the nexus between the... 

Ligation-Deligation Processes in Nickel-Reconstituted Heme Protejjns. In contrast with the 6-coordinate models, 5-coordinate sites of Hb and Mb show virtually no difference between the Raman spectra obtained with low and high powers for excitation at 420 nm. The undetectably low quantum yield for dissociation fo the nickel globins su ests that either (1) the dissociative state is not... 

Further mechanistic studies showed that no free peroxynitrite is formed during the reactions of NO with the oxy-forms of these proteins, and that nitrate is formed quantitatively, at both pH 7.0 and pH 9.0 [18]. Analysis of the proteins after ten cycles of oxidation by NO and reduction by ascorbic acid indicated that fewer than 1% of the tyrosine residues are nitrated. These results show that when peroxynitrite is coordinated to the heme of myoglobin or hemoglobin, it rapidly iso-merizes to nitrate, and thus cannot nitrate the tyrosine residues of the globin. 

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