Chittum H S, Champney W S
Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37232.
J Bacteriol. 1994 Oct;176(20):6192-8. doi: 10.1128/jb.176.20.6192-6198.1994.
The genes for ribosomal proteins L4 and L22 from two erythromycin-resistant mutants of Escherichia coli have been isolated and sequenced. In the L4 mutant, an A-to-G transition in codon 63 predicted a Lys-to-Glu change in the protein. In the L22 strain, a 9-bp deletion removed codons 82 to 84, eliminating the sequence Met-Lys-Arg from the protein. Consistent with these DNA changes, in comparison with wild-type proteins, both mutant proteins had reduced first-dimension mobilities in two-dimensional polyacrylamide gels. Complementation of each mutation by a wild-type gene on a plasmid vector resulted in increased erythromycin sensitivity in the partial-diploid strains. The fraction of ribosomes containing the mutant form of the protein was increased by growth in the presence of erythromycin. Erythromycin binding was increased by the fraction of wild-type protein present in the ribosome population. The strain with the L4 mutation was found to be cold sensitive for growth at 20 degrees C, and 50S-subunit assembly was impaired at this temperature. The mutated sequences are highly conserved in the corresponding proteins from a number of species. The results indicate the participation of these proteins in the interaction of erythromycin with the ribosome.
已从大肠杆菌的两个耐红霉素突变体中分离并测序了核糖体蛋白L4和L22的基因。在L4突变体中，密码子63处的A到G转换预测该蛋白中赖氨酸会变为谷氨酸。在L22菌株中，一个9碱基对的缺失去除了密码子82至84，使该蛋白中Met-Lys-Arg序列消失。与这些DNA变化一致，与野生型蛋白相比，两种突变蛋白在二维聚丙烯酰胺凝胶中的一维迁移率均降低。通过质粒载体上的野生型基因对每个突变进行互补，导致部分二倍体菌株对红霉素的敏感性增加。在红霉素存在下生长会增加含有该蛋白突变形式的核糖体比例。核糖体群体中野生型蛋白的比例增加了红霉素的结合。发现具有L4突变的菌株在20℃下生长对温度敏感，并且在此温度下50S亚基组装受损。突变序列在许多物种的相应蛋白中高度保守。结果表明这些蛋白参与了红霉素与核糖体的相互作用。
