Campuzano S, Vázquez D, Modolell J
Biochemistry. 1979 Apr 17;18(8):1570-4. doi: 10.1021/bi00575a029.
The spontaneous dissociation of complexes containing elongation factor G (EF-G), the ribosome, and either GDP plus fusidic acid, guanyl-5'-yl imidodiphosphate, or guanyl-5'-yl methylene diphosphonate has been measured and it follows biphasic kinetics that can be resolved into two first-order decay rates. This suggest the existence of two classes of complexes with apparent dissociation rate constants (k) differing 5--20-fold. The values of k and the distribution of complexes between the fast and the slowly decaying class depend on the conditions in which the dissociation occurs but not on the conditions in which the complexes are formed. Rapid transitions of complexes from one to the other class occur only when the chemical environment in which the dissociation takes place is modified. Thus, increasing the concentration of NH4Cl or adding the antibiotic thiostrepton accelerates the decay and converts slowly dissociating into fast dissociating complexes. In contrast, addition of misreading-inducing aminoglycoside antibiotics of the neomycin, kanamycin, streptomycin, and gentamicin (but not hygromycin) groups slows down the decay. For neomycin B at 10 micron, this effect is due to the conversion of fast into slowly decaying complexes. A model to explain the results involving conformational transitions of the complexes is proposed.
已对含有延伸因子G（EF - G）、核糖体以及GDP加夫西地酸、鸟苷 - 5'- 亚氨基二磷酸或鸟苷 - 5'- 亚甲基二磷酸的复合物的自发解离进行了测量，其遵循双相动力学，可分解为两个一级衰变率。这表明存在两类复合物，其表观解离速率常数（k）相差5至20倍。k的值以及快速和缓慢衰变类复合物之间的分布取决于解离发生时的条件，而不取决于复合物形成时的条件。只有当解离发生的化学环境发生改变时，复合物才会在两类之间快速转变。因此，增加氯化铵浓度或添加抗生素硫链丝菌素会加速衰变，并将缓慢解离的复合物转变为快速解离的复合物。相反，添加新霉素、卡那霉素、链霉素和庆大霉素（但不包括潮霉素）组的误读诱导型氨基糖苷类抗生素会减缓衰变。对于10微米的新霉素B，这种效应是由于快速衰变的复合物转变为缓慢衰变的复合物所致。提出了一个解释结果的模型，该模型涉及复合物的构象转变。
