Regulation of protein synthesis in rabbit reticulocyte lysates by the heme-regulated protein kinase: inhibition of interaction of Met-tRNAfMet binding factor with another initiation factor in formation of Met-tRNAfMet.40S ribosomal subunit complexes.
Regulation of protein synthesis in rabbit reticulocyte lysates by the heme-regulated protein kinase: inhibition of interaction of Met-tRNAfMet binding factor with another initiation factor in formation of Met-tRNAfMet.40S ribosomal subunit complexes.
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血红素调节蛋白激酶对兔网织红细胞裂解液中蛋白质合成的调节：抑制 Met-tRNAfMet 结合因子与形成 Met-tRNAfMet.40S 核糖体亚基复合物的另一个起始因子的相互作用。
DOI：
10.1073/pnas.75.2.745
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发表时间：
1978
影响因子：
11.1
通讯作者：
N. Gupta
中科院分区：
文献类型：
--
作者：
R. S. Ranu;I. London;A. Das;A. Dasgupta;A. Majumdar;R. Ralston;R. Roy;N. Gupta
网织红细胞及其裂解物中的蛋白质合成受血红素调节。在血红素缺乏症中，阻断多肽链起始的血红素调节的翻译抑制剂（HRI）被激活。HRI是一种蛋白激酶（ATP：蛋白磷酸转移酶，EC 2.7.1.37），其特异性磷酸化Met-tRNA（f）（Met）结合因子（IF）的38，000-道尔顿亚基，其与Met-tRNA（f）（Met）和GTP形成三元复合物，这一发现表明HRI的抑制涉及IF的磷酸化。我们研究了HRI在蛋白质链起始部分反应中的作用，其中IF促进的Met-tRNA（f）（Met）与40 S核糖体亚基的结合被另一个起始因子[三元复合物解离因子（TDF）]和AUC增强。结果表明，HRI在很低的浓度下显著抑制Met-tRNA（f）（Met）与40 S核糖体亚基的结合。HRI的抑制作用需要ATP。在这些条件下，HRI仅磷酸化IF的38，000-道尔顿亚基。TDF制剂不仅促进三元复合物与40 S亚基的结合，而且在0度下在5 mM Mg（2+）存在下促进三元复合物的解离。纯化的IF单独与低浓度的HRI和ATP的预孵育不显着影响其能力，形成三元复合物，但是，TDF-promoted的三元复合物的解离被抑制。不可水解的类似物腺苷5 '-[β，γ-亚氨基]三磷酸不能替代ATP。这些研究结果表明，磷酸化引起IF的构象修饰，这导致抑制三元复合物和TDF之间的相互作用，这是三元复合物与40 S亚基结合所需的。
Protein synthesis in reticulocytes and their lysates is regulated by heme. In heme deficiency a heme-regulated translational inhibitor (HRI) that blocks initiation of polypeptide chains is activated. HRI is a protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) that specifically phosphorylates the 38,000-dalton subunit of the Met-tRNA(f) (Met) binding factor (IF), which forms a ternary complex with Met-tRNA(f) (Met) and GTP, a finding that suggests that the inhibition by HRI involves the phosphorylation of IF. We have investigated the effect of HRI in the partial reactions of protein chain initiation in which the IF-promoted binding of Met-tRNA(f) (Met) to 40S ribosomal subunits is enhanced by another initiation factor [ternary complex dissociation factor (TDF)] and AUG. The results show that HRI at very low concentrations markedly inhibits the binding of Met-tRNA(f) (Met) to 40S subunits. The inhibitory effect of HRI requires ATP. Under these conditions HRI phosphorylates only the 38,000-dalton subunit of IF. The TDF preparations not only promote the binding of the ternary complex to 40S subunits but also promote the dissociation of the ternary complex in the presence of 5 mM Mg(2+) at 0 degrees . The preincubation of purified IF alone with low concentrations of HRI and ATP does not significantly affect its capacity to form the ternary complex; however, the TDF-promoted dissociation of the ternary complex is inhibited. The nonhydrolyzable analog adenosine 5'-[beta,gamma-imido]triphosphate does not substitute for ATP. These findings suggest that phosphorylation causes a conformational modification in IF, which results in inhibition of the interaction between the ternary complex and TDF that is required for the binding of the ternary complex to 40S subunits.