Molecular Biology 2nd Edition               Robert F. Weaver
		Student Resources

Chapter 19 See #1 under Chapter 18. Noller and colleagues have achieved a milestone in our understanding of the mechanism of protein synthesis. They have solved the crystal structure of the whole Thermus thermophilus ribosome, coupled to mRNA and tRNAs in all three sites, to molecular resolution. This study reveals many bridges between the two ribosomal subunits, and also between a subunit and a tRNA. These bridges are presumably important in many aspects of the translation process. (Yusupov, M.M., G. Zh. Yusupova, A. Baucom, K. Lieberman, T.N. Earnest, J.H.D. Cate, and H.F. Noller. 2001. Crystal structure of the ribosome at 5.5 resolution. Science 292:883-96) Ramakrishnan and colleagues have solved the crystal structure of the Thermus thermophilus 30S ribosomal subunit to 3.1-3.3 resolution, in the presence and absence of the antibiotic paromomycin. This antibiotic causes misreading of mRNAs, and has been thought to stabilize the flipping out of the bases of A1492 and A1493 of 16S rRNA, thus facilitating binding between mRNA and cognate (or non-cognate) tRNA. This study validates that model by showing that paromomycin really does cause the proposed base flipping. It also reveals that base G530 of the 16S rRNA and the ribosomal protein S12 make contact with base A1492. This accords with the long-appreciated role of base G530 and protein S12 in fidelity of translation. (Ogle, J.M., D.E. Brodersen, W. M. Clemons Jr., M.J. Tarry, A.P. Carter, and V. Ramakrishnan. 2001. Recognition of congnate transfer RNA by the 30S ribosomal subunit. Science 292:897-902)

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