Accuracy of TransferRNA Selection in Protein synthesis

ACCURACY OF TRANSFER RNA SELECTION IN PROTEIN SY The ribosome is a rapid magnificent molecular machine that plays an important role in proteinsynthesis and it consists of RNA and protein. The 70S bacterial ribosome comprises twosubunits, 30S and 50S. The 30S small subunit of the bacterial ribosome contains a protein calledS12, encoded by the rpsL gene. The function of this S12 protein is to help arrange the mRNAcorrectly to the ribosome and to interact with transfer RNA (tRNA) to initiate translation.Mutations in the rpsL gene generate phenotypes like resistance, dependence or pseudodependenceto the antibiotic streptomycin in bacteria. It is believed that mutations in the rpsLgene can increase the accuracy of tRNA selection in protein synthesis.The ribosome conducts the selection of tRNA in two steps: the initial selection and theproofreading step. During these multiple steps, the ribosome chooses the cognate aminoacyltRNAsin a ternary complex with EF-Tu and GTP and accommodates in the A site of ribosome.Therefore, the accuracy of the ribosome in selection of cognate aminoacyl-tRNA is crucial for the production of functional polypeptide sequences. Here, three different Escherichia coli strains; wild type MG1655, streptomycin restrictive (SmR) strain res222, and a streptomycin pseudo-dependent (SmP) strain w3110 are used, for studying the accuracy of tRNA selection inprotein synthesis. The mutant SmR shows hyper-accurate phenotype, which means, it has lowerpeptide bond formation efficiency and higher accuracy than the wild type. SmP shows pseudodependentto streptomycin phenotype which means it has higher peptide bond formation efficiency in the presence of antibiotic streptomycin. I have estimated the accuracy of tRNA selection in protein synthesis with enzyme kinetics. The kinetics data of these experiments display that mutant streptomycin restrictive is hyper-accurate and lower peptide bond formation efficiency than the wild type. SmP for the near cognate reaction in presence of antibiotic streptomycin has higher peptide bond formation efficiency than the SmP in absence of antibiotic streptomycin. SmP in presence antibiotic streptomycin has lower accuracy than the SmP in absence of antibiotic streptomycin