High resolution two-dimensional electrophoresis of proteins.

After infection and a prolonged incubation period, the scrapie agent causes a degenerative disease of the central nervous system in sheep and goats. Six lines of evidence including sensitivity to proteases demonstrate that this agent contains a protein that is required for infectivity. Although the scrapie agent is irreversibly inactivated by alkali, five procedures with more specificity for modifying nucleic acids failed to cause inactivation. The agent shows heterogeneity with respect to size, apparently a result of its hydrophobicity; the smallest form may have a molecular weight of 50,000 or less. Because the novel properties of the scrapie agent distinguish it from viruses, plasmids, and viroids, a new term "prion" is proposed to denote a small proteinaceous infectious particle which is resistant to inactivation by most procedures that modify nucleic acids. Knowledge of the scrapie agent structure may have significance for understanding the causes of several degenerative diseases.

http://science.sciencemag.org/content/sci/216/4542/136.full.pdf

Novel proteinaceous infectious particles cause scrapie

Genetic information encoded in messenger RNA is translated into protein by the ribosome, which is a large nucleoprotein complex comprising two subunits, denoted 30S and 50S in bacteria. Here we report the crystal structure of the 30S subunit from Thermus thermophilus, refined to 3 A resolution. The final atomic model rationalizes over four decades of biochemical data on the ribosome, and provides a wealth of information about RNA and protein structure, protein–RNA interactions and ribosome assembly. It is also a structural basis for analysis of the functions of the 30S subunit, such as decoding, and for understanding the action of antibiotics. The structure will facilitate the interpretation in molecular terms of lower resolution structural data on several functional states of the ribosome from electron microscopy and crystallography.

Structure of the 30S ribosomal subunit.

Dangerous, antibiotic resistant bacteria have been observed with increasing frequency over the past several decades. In this review the factors that have been linked to this phenomenon are addressed. Profiles of bacterial species that are deemed to be particularly concerning at the present time are illustrated. Factors including economic impact, intrinsic and acquired drug resistance, morbidity and mortality rates, and means of infection are taken into account. Synchronously with the waxing of bacterial resistance there has been waning antibiotic development. The approaches that scientists are employing in the pursuit of new antibacterial agents are briefly described. The standings of established antibiotic classes as well as potentially emerging classes are assessed with an emphasis on molecules that have been clinically approved or are in advanced stages of development. Historical perspectives, mechanisms of action and resistance, spectrum of activity, and preeminent members of each class are discussed.

Antibiotics and Bacterial Resistance in the 21st Century

Modulation of Chemical Composition and Other Parameters of the Cell by Growth Rate

PERSPECTIVES AND SUMMARY . ...... ..... . .... ..... ..... ...... 155 RIBOSOMAL PROTEINS ....... ......... ...... ... .... ..... ..... . ..... . .... ... . . ......... . .. .. .. ....... 156 Primary Structure 156 Secondary Structure ......... ..... ......... ... ..... ...... ..... ... 160 Tertiary Structure .... .. ...... ..... ..... ..... ........ ....... ..... 161 Limited proteolysis ..... ... ......... ..... ..... ... ..... ..... ...... ......... .... 161 Proton magnetic resonance ....... ..... .... 162 Crystallization .. ........ ..... ....... 164 Shape 164 RIBOSOMAL RNAs ..... ......... .... ..... . .. ... ..... ...... ..... ..... ..... .... .. .... . ... 167 5S RNA 168 5S RNA from E. coli ......... ..... .. ........ ...... ...... ...... 168 5S RNA from other bacteria .... ...... .... ..... ...... ...... ...... ....... 170 16S RNA 172 Primary and secondary structures . .... ..... ..... ..... ...... 172 Protein binding sites on the 16S RNA ...... . . ... . .... ..... 174 23S RNA 176 Primary and secondary struclures 176 Protein binding sites on the 23S RNA 177

Components of bacterial ribosomes

Architecture of Prokaryotic Ribosomes

Ribosomes from nine E. coli mutants with high level resistance to the antibiotic erythromycin were isolated and their proteins were compared with those of the parental strains by two-dimensional polyacrylamide gel electrophoresis, by carboxymethylcellulose column chromatography and by immunological techniques. Two 50S proteins were found to be altered in the mutants: either L 4 or L 22.

Biochemical and genetic studies on two different types of erythromycin resistant mutants of Escherichia coli with altered ribosomal proteins.

Ribosomal proteins. Isolation of the proteins from 30S ribosomal subunits of Escherichia coli.

Ribosomal proteins isolated from 30S subunits ofE. coli in four laboratories have been correlated by using two-dimensional gel electrophoresis, immunological techniques, amino acid compositions and molecular weights. The results are given in the Table. A common nomenclature for naming 30 S ribosomal proteins and their genetic loci is proposed.

H. G. Wittmann

Papers

Components of bacterial ribosomes

Architecture of Prokaryotic Ribosomes

Biochemical and genetic studies on two different types of erythromycin resistant mutants of Escherichia coli with altered ribosomal proteins.

Ribosomal proteins. Isolation of the proteins from 30S ribosomal subunits of Escherichia coli.

Correlation of 30S ribosomal proteins of Escherichia coli isolated in different laboratories.