The P-Site Loop of the Universally Conserved Bacterial Ribosomal Protein L5 Is Required for Maintaining Both...

The bacterial ribosomal 5S rRNA-binding protein L5 is universally conserved (uL5). It contains the so-called P-site loop (PSL), which contacts the P-site tRNA in the ribosome. Certain PSL mutations in yeast are lethal, suggesting that the loop plays an important role in translation. In this work, for the first time, a viable Escherichia coli strain was obtained with the deletion of the major part of the PSL (residues 73-80) of the uL5 protein. The deletion conferred cold sensitivity and drastically reduced the growth rate and overall protein synthesizing capacity of the mutant. Translation rate is decreased in mutant cells as compared to the control. At the same time, the deletion causes increased levels of -1 frameshifting and readthrough of all three stop codons. In general, the results show that the PSL of the uL5 is required for maintaining both the accuracy and rate of protein synthesis in vivo.