RELATIONSHIP BETWEEN PHOSPHORYLATION AND ACTIVITY OF HEME-REGULATED EUKARYOTIC INITIATION-FACTOR 2-ALPHA KINASE
RELATIONSHIP BETWEEN PHOSPHORYLATION AND ACTIVITY OF HEME-REGULATED EUKARYOTIC INITIATION-FACTOR 2-ALPHA KINASE
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DOI：
10.1073/pnas.78.2.866
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发表时间：
1981-01-01
期刊：
影响因子：
--
通讯作者：
LONDON, IM
中科院分区：
文献类型：
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作者：
FAGARD, R;LONDON, IM
在血红素缺乏的兔网织红细胞及其裂解物中，血红素调节的蛋白质合成抑制剂被激活；该抑制剂是一种不依赖于 cAMP 的蛋白激酶，可特异性磷酸化 .alpha。真核起始因子 2 (eIF-2.alpha.) 的亚基。血红素通过抑制激酶的激活和活性来调节该激酶。纯化的血红素调节激酶 (HRI) 发生自磷酸化；每个 HRI 亚基（MW 80,000）可以掺入至少 3 mol 磷酸盐。 HRI 的磷酸化，即 eIF-2.alpha。激酶活性及其抑制蛋白质合成的能力会被氯高铁血红素 (5 mM) 减弱，并被 N-乙基马来酰亚胺 (MalNEt) 增强。用氯化血红素处理 MalNEt 激活的 HRI 会降低其自身磷酸化及其抑制蛋白质合成的能力。这些发现证明了 HRI 的磷酸化及其 eIF-2.alpha 的相关性。激酶活性及其对蛋白质合成的抑制。通过检测氯化血红素与纯化的 HRI 的结合，研究了氯化血红素调节 HRI 活性的机制。通过差异光谱法可以证明显着的结合，该光谱揭示了血红素的吸收光谱的显着变化，在 418 nm 处出现了峰，这种变化与已知结合血红素的蛋白质所观察到的变化类似。这些发现与氯高铁血红素对 HRI 的直接影响一致。
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.