Van Delft J H, Bosch L
Department of Biochemistry, University of Leiden, The Netherlands.
Eur J Biochem. 1988 Aug 1;175(2):375-8. doi: 10.1111/j.1432-1033.1988.tb14206.x.
The expression of tufB, one of the two EF-Tu-encoding genes in Escherichia coli, is under autogenous control. Feedback inhibition of tufB expression by plasmid-borne EF-Tu has been used to answer the question of whether or not the integrity of the guanine-nucleotide-binding domain of EF-Tu is required for the autoregulatory role of the factor protein. We show that a large deletion of tufB, causing the elimination of an 81-amino-acid segment from the plasmid-borne EF-Tu, does not abolish tufB repression. We conclude that the autoregulation of the cellular EF-Tu level is not dependent on an intact guanine-nucleotide-binding domain and does not require binding of GTP to EF-Tu. The repressor activity of the deletion derivative of EF-Tu can be measured despite a rapid disappearance of the (altered) mutant protein from the soluble cytoplasmic fraction of the cell. Degradation and assembly in larger complexes are responsible for this disappearance.
tufB是大肠杆菌中两个编码EF-Tu的基因之一，其表达受自身调控。利用质粒携带的EF-Tu对tufB表达的反馈抑制来回答EF-Tu鸟嘌呤核苷酸结合结构域的完整性对于该因子蛋白的自调控作用是否必需这一问题。我们发现，tufB的大片段缺失导致质粒携带的EF-Tu中一个81个氨基酸的片段被去除，但这并未消除tufB的抑制作用。我们得出结论，细胞内EF-Tu水平的自调控不依赖于完整的鸟嘌呤核苷酸结合结构域，也不需要GTP与EF-Tu结合。尽管（改变后的）突变蛋白在细胞可溶性细胞质部分中迅速消失，但仍可检测到EF-Tu缺失衍生物的阻遏活性。这种消失是由降解和组装成更大的复合物导致的。
