Secondary structure of tobacco mosaic virus protein

A set of rules is proposed for the prediction of α-helices in proteins. These rules lead to the correct assignment to either helical or non-helical regions of over 80% of the amino acid residues in the proteins from which they are derived. Applied to tobacco mosaic virus protein these rules lead to the prediction of five α-helical regions which may be consistent with other data

ELONGATION FACTOR-T FROM BACILLUS-STEAROTHERMOPHILUS AND ESCHERICHIA-COLI - PURIFICATION AND SOME PROPERTIES OF EF-TU AND EF-TS FROM BACILLUS-STEAROTHERMOPHILUS

Homogeneous preparations of elongation factors EF‐Tu and EF‐Ts from Bacillus stearothermophilus have been obtained with specific activities of 20000 ± 2000 and 500000 ± 50 000 units/ mg, respectively. By dodecylsulphate‐polyacrylamide gel electrophoresis the molecular weight of EF‐Tu was found to be 49000 ± 2000 and of EF‐Ts 35500 ± 1000. Nucleotide‐free EF‐Tu was prepared by using ITP as a GDP‐binding‐site‐directed analogue. EF‐Tu was shown to contain two sulphydryl groups, one reacting fast and one slowly with N‐ethylmaleimide and 5,5′‐dithio‐bis(2nitrobenzoic acid) under non‐denaturing conditions. The same reagents were shown to react with the three sulphydryl groups of EF‐Ts in the native state. The heat stabilities of EF‐Tu and EF‐Ts are reversed with respect to the Escherichia coli factors, EF‐Tu being the more stable protein; even nucleotide‐free EF‐Tu is relatively stable with a half‐life at room temperature of about 35 h

The structures of turnip crinkle and tomato bushy stunt viruses: I. A small protein particle derived from turnip crinkle virus

A small protein particle can be produced by degrading turnip crinkle virus. This particle has a diameter of 200 Å compared with 330 Å for the virus particle and could either be a virus core or a reaggregation product. The small particle appears to be composed only of protein which is identical or very similar to the protein of the whole virus. No chemical evidence has been obtained for the hypothesis that the small particles are virus cores but their assembly from virus protein can easily be demonstrated

EFFECT OF MG²⁺ ON SOME PROPERTIES OF NUCLEOTIDE-FREE ELONGATION-FACTOR TU FROM BACILLUS-STEAROTHERMOPHILUS

The nucleotide‐free elongation factor from Bacillus stearothermophilus provides a means to study the effect of Mg2+ ions on various reactions of the protein. The binding of GDP to the protein is stimulated by Mg2+. From comparative studies with other metal ions, particularly Mn2+, it appears that this stimulation is due to the formation of a metal · GDP complex which is bound to the protein. Protection against proteolysis by trypsin is afforded by both Mg2+ and Mg · GDP, but not by GDP alone. The rate of substitution of the sulphydryl group associated with aminoacyl‐tRNA binding, by either 5,5′‐dithio‐bis(2‐nitrobenzoic acid) or N‐ethylmaleimide is reduced in the presence of Mg2+. All these observations show that Mg2+ not only is involved in GDP binding but also has a direct effect on the tertiary structure of the protein