Herrera F, Correia H, Triana L, Fraile G
Centro de Investigaciones Biomédicas (BIOMED), Facultad de Ciencias de la Salud, Universidad de Carabobo, Venezuela.
Eur J Biochem. 1991 Sep 1;200(2):321-7. doi: 10.1111/j.1432-1033.1991.tb16188.x.
A yeast ribosomal subunit association factor (AF) has been purified from a high-salt ribosomal wash. The purified enzyme is a thermostable protein that associates ribosomal subunits at low Mg2+ concentration without requiring energy. It appears to be an aggregate of trimers or dimers (molecular mass 125 or 79 kDa) which on sodium dodecyl sulfate gels shows the presence of a major protein band whose estimated molecular mass is 43 kDa. Evidence also indicates the existence of a 50-kDa polypeptide which seems to be unstable since with freezing and thawing it gives rise to the 43-kDa polypeptide. It was shown that the labelled factor interacts with 80S ribosomes and with 40S ribosomal subunits. The purified polypeptide reacts with antibodies directed against EF-1 alpha, this last protein recognizing the antibodies raised against AF. Likewise, both EF-1 alpha and AF associate ribosomal subunits in the same way. When EF-1 is heated, it not only maintains its association activity, but also behaves like a 43-kDa polypeptide in an SDS electrophoresis run. These observations strongly suggest that AF originates from EF-1 alpha, which implies that the well-known elongation factor may also play a role in the initiation step of protein synthesis.
一种酵母核糖体亚基结合因子（AF）已从高盐核糖体洗涤液中纯化出来。纯化后的酶是一种热稳定蛋白，能在低镁离子浓度下结合核糖体亚基，且无需能量。它似乎是三聚体或二聚体的聚集体（分子量分别为125或79 kDa），在十二烷基硫酸钠凝胶上显示出一条主要蛋白带，其估计分子量为43 kDa。证据还表明存在一种50 kDa的多肽，它似乎不稳定，因为经冻融后会产生43 kDa的多肽。结果表明，标记的因子与80S核糖体和40S核糖体亚基相互作用。纯化后的多肽与针对EF-1α的抗体发生反应，而最后这种蛋白能识别针对AF产生的抗体。同样，EF-1α和AF以相同方式结合核糖体亚基。当EF-1加热时，它不仅保持其结合活性，而且在SDS电泳中表现得像一种43 kDa的多肽。这些观察结果强烈表明AF源自EF-1α，这意味着这种著名的延伸因子可能在蛋白质合成的起始步骤中也发挥作用。
