Major groove binding of the tRNA/mRNA complex to the 16 S ribosomal RNA decoding site.

We propose a detailed three-dimensional model, with atomic detail, for the structure of the Escherichia coli 16 S rRNA decoding site in a complex with mRNA and the A and P-site tRNAs. Model building began with four primary assumptions: (1) A and P-site tRNA conformations are identical with those seen in the tRNA crystal structure; (2) A and P-site tRNAs adopt an S-type orientation upon binding mRNA in the ribosome; (3) A1492 and A1493 bind non-specifically to the mRNA through a series of hydrogen bonds; and (4) C1400 lies in close proximity to the P-site tRNA wobble base in order to satisfy a UV-induced photocrosslink formed between the two residues. We have models with both major groove and minor groove binding of the tRNA/mRNA complex to the decoding site RNA, and conclude that major groove binding is more likely.

Ribonuclease P RNA: models of the 15/16 bulge from Escherichia coli and the P15 stem loop of Bacillus subtilis.

The Escherichia coli ribonuclease P RNA 15/16 internal bulge loop and the Bacillus subtilis P15 stem loop are important substrate binding sites for the CCA-3' terminus of pre-tRNA. Models of E. coli 15/16 bulge loop and the B.

Modeling the structure of the ribosome.

Considering the size and complexity of the ribosome and the growing body of data from a wide range of experiments on ribosomal structure, it is becoming increasingly important to develop tools that facilitate the development of reliable models for the ribosome. We use a combination of manual and computer-based approaches for building and refining models of the ribosome and other RNA-protein complexes. Our methods are aimed at determining the range of models compatible with the data, making quantitative statements about the positional uncertainties (resolution) of different regions, identifying conflicts in the data, establishing which regions of the ribosome need further experimental exploration, and, where possible, predicting the outcome of future experiments.

Orientations of transfer RNA in the ribosomal A and P sites.

In protein synthesis, peptide bond formation requires that the tRNA carrying the amino acid (A site tRNA) contact the tRNA carrying the growing peptide chain (P site tRNA) at their 3' termini. Two models have been proposed for the orientations of two tRNAs as they would be bound to the mRNA in the ribosome. Viewing the tRNA as an upside down L, anticodon loop pointing down, acceptor stem pointing right, and calling this the front view, the R (Rich) model would have the back of the P site tRNA facing the front of the A site tRNA.