Protein-RNA Interactions in the Ribosome

点击翻译按钮获取中文摘要

9818051The expression of genetic information in all cells depends on specific, noncovalent interactions between protein and RNA molecules. Nowhere is the importance of such interactions better illustrated than in ribosomes, the complex ribonucleoprotein particles that carry out the biosynthesis of cellular proteins according to genetic information encoded in messenger RNA. Ribosomal particles are composed of roughly 55 different proteins, two large RNA molecules, and one small RNA molecule which assemble into a compact, functional structure owing to an intricate network of noncovalent protein-RNA interactions. Specific associations between ribosomal proteins and ribosomal RNAs are essential both for the assembly and for the structural integrity of the ribosome, and underlie the functional activity of this particle in protein synthesis. In the bacterium Escherichia coli, many of the proteins that associate with ribosomal RNA also regulate the expression of the ribosomal protein genes through specific interactions with the corresponding messenger RNAs. These complexes provide a rich source of material for investigating the molecular bases of protein-RNA interaction. The present research is directed toward elucidating the specific structural features that mediate the association of small-subunit protein S8 with its binding site in 16S ribosomal RNA and of large-subunit protein L1 with its binding site in 23S ribosomal RNA. Each of the protein binding sites has been narrowed down to about 30 nucleotides and that for protein S8 has been solved by NMR. Further insight into the nature of the S8- and L1-RNA interactions will be gained through site-directed mutagenesis, protein-RNA cross-linking, functional group analysis, SELEX, NMR and X-ray crystallography. Precise information about the structure of ribosomal protein-rRNA complexes is important not only for understanding the way in which several dozen unique ribosomal components spontaneously assemble into functional ribonucleoprotein particles, but also for comprehending the principles that underlie the many different protein-RNA interactions that play crucial roles in the expression of genetic information via the synthesis of DNA, RNA and protein molecules.The expression of the genetic information stored in the DNA culminates in the synthesis of the proteins that define the properties of individual cells. Remarkably, the mechanism of this process is quite similar in all organisms, from bacteria to humans. Protein synthesis is carried out by compact globular particles known as ribosomes which consist of a large number of protein and RNA molecules arranged in an intricate and highly specific manner. The ribosomal particles guide the assembly of many other cellular components on its surface in a way that permits the efficient linkage of amino acids into protein chains according to the genetic plans encoded in the DNA. Ribosome function in protein synthesis depends critically on the precise three-dimensional structure that these particles assume. The structure of the ribosome is in turn determined by a myriad of chemical interactions among its protein and RNA components. The main objective of this research is to gain a better understanding of such interactions by determining the molecular architecture of some of the protein-RNA complexes that underlie the three-dimensional structure of the ribosomal particle. The results will help to explain the manner in which the structure of the ribosome contributes to its function in protein synthesis.