Relationship between phosphorylation and activity of heme-regulated eukaryotic initiation factor 2 alpha kinase.
- 1 February 1981
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 78 (2) , 866-870
- https://doi.org/10.1073/pnas.78.2.866
Abstract
In heme-deficient rabbit reticulocytes and their lysates, a heme-regulated inhibitor of protein synthesis is activated; this inhibitor is a cAMP-independent protein kinase that specifically phosphorylates the .alpha. subunit of the eukaryotic initiation factor 2 (eIF-2.alpha.). Heme regulates this kinase by inhibiting its activation and activity. The purified heme-regulated kinase (HRI) undergoes autophosphorylation; at least 3 mol of phosphate can be incorporated/HRI subunit (MW 80,000). The phosphorylation of HRI, its eIF-2.alpha. kinase activity and its ability to inhibit protein synthesis are diminished by hemin (5 mM) and increased by N-ethylmaleimide (MalNEt). Treatment of MalNEt-activated HRI with hemin reduces its autophosphorylation and its ability to inhibit protein synthesis. These findings demonstrate a correlation of the phosphorylaton of HRI, its eIF-2.alpha. kinase activity and its inhibition of protein synthesis. The mechanism of hemin regulation of HRI activity was studied by examining the binding of hemin to purified HRI. Significant binding was demonstrable by difference spectroscopy which revealed a pronounced shift in the absorption spectrum of hemin with the appearance of a peak at 418 nm, a shift similar to that observed with proteins known to bind hemin. These findings are consistent with a direct effect of hemin on HRI.This publication has 26 references indexed in Scilit:
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