Kabat D
J Biol Chem. 1975 Aug 10;250(15):6085-92.
The polyadenylic acid-containing messenger ribonucleic acid from rabbit reticulocyte polyribosomes, isolated by a rapid and very gentle procedure (Krystosek, A., Cawthon, M. L., and Kabat, D. (1975) J. Biol. Chem. 250, 6077-6084), sediments in a sucrose gradient in three sharp peaks, at 9 S, 17 to 18 S, and 28 S. The alpha and beta globin messenger activity follows the absorbance profile in the sucrose gradients and has its major peak at 17 to 18 S. The larger messengers are more active than 9 S messenger by approximately 2-fold per mass unit of ribonucleic acid or by at least 8-fold per molecule. The major 17 to 18 S form of globin messenger was examined further and was shown to be a 1:1 complex of 9 S messenger and 18 S ribosomal ribonucleic acid. The effect of 18 S ribosomal ribonucleic acid on translation of purified 9 S globin messenger was analyzed in a messenger-dependent protein-synthesizing system (Krystosek, A., Cawthon, M. L., and Kabat, D. (1975) J. Biol. Chem. 250, 6077-6084). In the absence of exogenous ribosomal ribonucleic acid, 9 S messenger is inefficiently translated; a large excess of messenger is required to saturate the system; and globin is synthesized mainly on di- and monoribosomes. Exogenous liver or reticulocyte 18 S ribosomal ribonucleic acid potentiates 9 S messenger translation and renders it at least 10 times more efficient. The potentiation reaction can also be accomplished by increasing the concentration of ribosomes in the assay system. However, transfer or messenger ribonucleic acids cannot carry out this reaction. It is proposed that 9 S globin messenger ribonucleic acid is an inactive molecule which is normally potentiated by specific reversible base pairing with an accessible region of ribosomal ribonucleic acid contained in a 40 S ribosomal subunit. The potentiated messenger interacts with initiation factors and with other ribosomal subunits to synthesize protein. Potentiation is the first specific function in protein synthesis demonstrated for the ribosomal ribonucleic acid portion of ribosomes.
通过一种快速且温和的方法（克里斯托塞克，A.，考索恩，M. L.，和卡巴特，D.（1975年）《生物化学杂志》250，6077 - 6084）从兔网织红细胞多核糖体中分离得到的含多聚腺苷酸的信使核糖核酸，在蔗糖梯度中沉降出三个尖锐峰，分别在9 S、17至18 S和28 S处。α和β珠蛋白信使活性与蔗糖梯度中的吸光度曲线一致，其主峰在17至18 S处。较大的信使每单位质量的核糖核酸比9 S信使的活性大约高2倍，或每分子至少高8倍。对主要的17至18 S形式的珠蛋白信使进行了进一步研究，结果表明它是9 S信使与18 S核糖体核糖核酸的1:1复合物。在一个依赖信使的蛋白质合成系统中（克里斯托塞克，A.，考索恩，M. L.，和卡巴特，D.（1975年）《生物化学杂志》250，6077 - 6084）分析了18 S核糖体核糖核酸对纯化的9 S珠蛋白信使翻译的影响。在没有外源核糖体核糖核酸的情况下，9 S信使的翻译效率低下；需要大量过量的信使才能使系统饱和；并且珠蛋白主要在二核糖体和单核糖体上合成。外源肝脏或网织红细胞的18 S核糖体核糖核酸增强了9 S信使的翻译，使其效率至少提高10倍。增强反应也可以通过增加测定系统中核糖体的浓度来实现。然而，转移核糖核酸或信使核糖核酸不能进行此反应。有人提出，9 S珠蛋白信使核糖核酸是一种无活性分子，通常通过与40 S核糖体亚基中所含核糖体核糖核酸的可及区域进行特异性可逆碱基配对而被增强。增强后的信使与起始因子以及其他核糖体亚基相互作用以合成蛋白质。增强作用是核糖体的核糖体核糖核酸部分在蛋白质合成中展示出的第一个特定功能。
