REGULATION OF EUKARYOTIC PROTEIN SYNTHESIS INITIATION

真核生物中蛋白质合成的起始是 通过一系列最复杂的生化反应 已知的反应 了解这一过程对于 了解蛋白质合成的速率是如何调节的， 许多病毒的细胞毒性作用，抗病毒药物的作用， 蛋白质干扰素，以及基因的最终表达， 信息. 该项目的长期目标有两个- 折叠：了解各种蛋白质的生化作用（elF- 4组起始因子）参与信使RNA的进入 进入启动过程，并启动因素负责 起始因子的活性和表达水平 eIF-4 E（帽结合蛋白）。 对于第一个目标， eIF-4 E位点将通过两种技术的组合来确定： 一组新的光亲和标记将被合成并用于 标记eIF-4 E的m7 GTP结合位点。 第二，改变形式 eIF-4 E将通过定点诱变在体外产生。 的 eIF-4A、-4B、-4E和-4F在不同起始点上的位置 复合体将被确定。 帽盖结构的相互作用， 在mRNA和m7 GTP的光亲和衍生物中， 将研究eIF-4组因素。 最后， eIF-4F的p220组分将被克隆和测序。 为 第二个目的，eIF-4 E磷酸化的作用将是 考察 这将在体外研究，通过使用 特异性激酶和通过无细胞合成形式的eIF-4 E 缺乏磷酸化位点，由定点 诱变 它也将在体内进行研究， 磷酸化与蛋白质合成速率和使用瞬时 含有诱变形式的eIF-4 E cDNA的表达载体。 最后，各种形式的eIF-4 E mRNA的结构将 进行检查，并将克隆这种蛋白质的基因， 部分排序。 R0GM33804 选定的功能特性， 细胞色素c将被调查和可能的捐赠 将探索这种具有新功能特性的蛋白质 通过建造一系列专门设计的 突变体如下：（1）推定的晶体学 在所述表面上的底物结合位点的鉴定 Ser-82变异体将通过检查 相关小分子对氧化还原性能的影响 蛋白质。(2)轴向配体在决定 将通过分析Met-80突变体来研究细胞色素功能。 (3)38和82位突变改变 碱性转变将通过pH跳跃实验、EPR 光谱学和静电学计算。 (4)高野 细胞色素c氧化还原相互转换的迪克森模型将是 通过研究最近构建的Thr-78突变体进行评估。 这 残留物对Takano-Dickerson模型至关重要，因为它是氢- 与一个至关重要的内部水分子结合， 他们的提议。 (5)血红素丙酸酯-7在调节 蛋白质的还原电位将通过 考虑Tyr-48突变体。 Tyr-48/Arg-的可能分析 在这方面也将考虑38个双突变体。 （六） 将进一步分析Phe-82的多重作用 通过评价在该位置构建的几种新突变体。 (7)细胞色素之间的物种差异的起源将是 通过回路的构造和表征来考虑 转化酵母iso-l细胞色素c插入/缺失突变体 变成大小接近两个原核细胞色素的形式。 (8)的 选择性突变对电子转移动力学的影响 生理氧化还原伴侣蛋白质将被研究。 (9)一 光谱技术（NMR，CD/MCD和时间分辨） 荧光光谱法）将应用于选定的突变体， 由其观察到的性质决定。

Initiation of protein synthesis in eukaryotic organisms is accomplished through one of the most complex series of biochemical reaction known. Knowledge of this process is important for an understanding of how the rate of protein synthesis is regulated, the cytotoxic effect of many viruses, the action of the antiviral protein interferon, and the ultimate expression of genetic information. The long-term objectives of this project are two- fold: to understand the biochemical roles of various proteins (elF- 4 group initiation factors) involved in the entry of messenger RNA into the initiation process, and to initiation factors responsible for the activity and level of expression of the initiation factor eIF-4E (cap-binding protein). For the first objective, the active site of eIF-4E will be determined by a combination two techniques: a set of new photoaffinity labels will be synthesized and used to label the m7GTP-binding site of eIF-4E. Second, altered forms of eIF-4E will be produced in vitro by site-directed mutagenesis. The location of eIF-4A, -4B, -4E and -4F on various initiation complexes will be determined. The interaction of cap structures, both in mRNA and in photoaffinity derivatives of m7GTP, with the eIF-4 group factors will be investigated. Finally, the cDNA for the p220 component of eIF-4F will be cloned and sequenced. For the second objective, the effect of phosphorylation of eIF-4E will be examined. This will be studied in vitro through the use of specific kinase and by cell-free synthesis of forms of eIF-4E lacking a phosphorylation site, produced by site-directed mutagenesis. It will also be studied in vivo, by correlating phosphorylation with protein synthesis rates and by using transient expression vectors containing mutagenized forms of eIF-4E cDNA. Finally, the structure of the various forms of eIF-4E mRNA will be examined, and the gene for this protein will be cloned and partially sequenced. R0GM33804 Selected functional properties that are characteristic of cytochrome c will be investigated and the possible endowment of this protein with new functional properties will be explored through the construction of a series of specifically designed mutants as follows: (1) The putative crystallographic identification of a substrate binding site on the surface of the Ser-82 variant will be evaluated by examination of the effect of relevant small molecules on the oxidation-reduction properties of the protein. (2) The role of the axial ligands in determining cytochrome function will be studied by analysis of Met-80 mutants. (3) The mechanism by which mutations at positions 38 and 82 alter the alkaline transition will be studied by pH-jump experiments, EPR spectroscopy, and electrostatics calculations. (4) The Takano Dickerson model for cytochrome c redox interconversion will be evaluated by study of recently constructed Thr-78 mutants. This residue is critical to the Takano-Dickerson model as it hydrogen- bonds to a crucial, internally-bound water molecule that is pivotal to their proposal. (5) The role of heme propionate-7 in regulating the reduction potential of the protein will be studied by consideration of a Tyr-48 mutant. Possible analysis of Tyr-48/Arg- 38 double mutants will be considered in this regard as well. (6) Further analysis of the multiple roles of Phe-82 will be analyzed by evaluation of several new mutants constructed at this position. (7) The origin of species differences between cytochromes will be considered through construction and characterization of loop insertion/deletion mutants which convert yeast iso-l cytochrome c into forms closer in size to two prokaryotic cytochromes. (8) The effects of selected mutations on the kinetics of electron transfer to physiological redox partner proteins will be studied. (9) A battery of spectroscopic techniques (NMR, CD/MCD, and time-resolved fluorescence spectroscopy) will be applied to selected mutants as dictated by their observed properties.