Saha S K, Chakraburtty K
J Biol Chem. 1986 Sep 25;261(27):12599-603.
Two species of the elongation factor 1 (EF-1) differing in molecular weight, subunit composition, and isoelectric point have been isolated from cell-free extracts of the yeast Saccharomyces cerevisiae. The ratio of these two forms of EF-1 activity (EF-1 alpha and EF-1H) seem to vary in different strains and upon the growth phase from which the cells have been isolated. The log phase cells of a protease negative yeast strain EJ101 show a distribution of EF-1 alpha and EF-1H in the ratio of 3:1. Another laboratory yeast strain, D-587-4B, shows a distribution pattern of 4:1. The two forms of EF-1 are completely separable by ion exchange, gel permeation, and hydrophobic and affinity chromatography. Yeast EF-1 alpha is a single polypeptide of molecular weight 50,000 and has an isoelectric point of 8.9. The newly identified form of the yeast EF-1 (EF-1H) has a molecular weight of 200,000. The isoelectric point of this protein is around 5.5. Electrophoresis of the partially purified EF-1H in polyacrylamide gel containing sodium dodecyl sulfate indicates the presence of three nonidentical polypeptides having molecular weights of 50,000, 47,000, and 33,000. The three polypeptides are present in the ratio of 2:1:1. EF-1H is readily converted to EF-1 alpha and EF-1 beta gamma on anion exchange columns. The 50,000 dalton component of EF-1H immunologically cross-reacts with the antibody to EF-1 alpha. The other two polypeptides do not. On the basis of molecular weight, EF-1H is 2-3-fold more active than EF-1 alpha in poly(U)-dependent polyphenylalanine synthesis. EF-1H exchanges nucleotide (GDP----GTP) at a faster rate than EF-1 alpha. Both EF-1 alpha and EF-1H exhibit similar binding constants for GDP and GTP although the affinity of EF-1 alpha for guanine nucleotides is several-fold higher than that of EF-1H. The 33,000-dalton component of EF-1H appears to be functionally analogous to EF-1 beta (Ts) isolated from other eukaryotic sources. The function of EF-1 gamma is unknown.
从酿酒酵母的无细胞提取物中分离出了两种延伸因子1（EF-1），它们在分子量、亚基组成和等电点上存在差异。这两种形式的EF-1活性（EF-1α和EF-1H）的比例似乎在不同菌株以及分离细胞的生长阶段有所不同。蛋白酶阴性酵母菌株EJ101的对数期细胞中，EF-1α和EF-1H的分布比例为3:1。另一种实验室酵母菌株D-587-4B的分布模式为4:1。通过离子交换、凝胶渗透、疏水和亲和层析可将这两种形式的EF-1完全分离。酵母EF-1α是一种分子量为50,000的单一多肽，等电点为8.9。新鉴定出的酵母EF-1形式（EF-1H）分子量为200,000。该蛋白的等电点约为5.5。在含有十二烷基硫酸钠的聚丙烯酰胺凝胶中对部分纯化的EF-1H进行电泳，结果表明存在三种分子量分别为50,000、47,000和33,000的不同多肽。这三种多肽的比例为2:1:1。EF-1H在阴离子交换柱上很容易转化为EF-1α和EF-1βγ。EF-1H的50,000道尔顿组分与针对EF-1α的抗体发生免疫交叉反应。另外两种多肽则不会。基于分子量，在依赖多聚尿苷酸的聚苯丙氨酸合成中，EF-1H的活性比EF-1α高2至3倍。EF-1H交换核苷酸（GDP→GTP）的速度比EF-1α快。尽管EF-1α对鸟嘌呤核苷酸的亲和力比EF-1H高几倍，但EF-1α和EF-1H对GDP和GTP的结合常数相似。EF-1H的33,000道尔顿组分在功能上似乎类似于从其他真核生物来源分离出的EF-1β（Ts）。EF-1γ的功能尚不清楚。
