Morton P. Printz

Evidence for conformational changes in elongation factor Tu induced by GTP and GDP.

Abstract A comparative study of the rates of tritium-hydrogen exchange in three liganded states of the protein elongation factor Tu (EFTu) reveals a substantial conformational difference between the free (EFTu) or GTP-bound (EFTu·GTP) forms and when GDP is present (EFTu·GDP). This conformational difference is acentuated with short time tritiations. There are 25–35% more very slow hydrogens in EFTu·GDP than in EFTu·GTP, indicating that GDP induces a tighter conformation in EFTu than does GTP . Thus, a rationale is provided for the difference in reactivity of EFTu·GTP and EFTu·GDP for AA-tRNA and a conformational role in regulating protein biosynthesis may be proposed for GTP and GDP. Finally, we demonstrate that nucleoside polyphosphates may cause size-able conformational changes in proteins.

Modification of an isco drum fraction collector to permit use of stoppered test tubes

Abstract An automatically stoppering test tube fraction collector is described. While the unit was designed for an Isco collector system, the design can be readily adapted to any existing drum fraction collector. The system as used prevents both significant loss of solvent from 300-μl column fractions and radioactive cross contamination of volatile isotopic compounds.

Studies on the mode of self-association of tyrocidin B

Abstract Experiments on the self-association of dialyzed solutions of tyrocidine B have been performed in the ultracentrifuge. The data were analyzed by the two-species plot technique, and give evidence for the hypothesis that tyrocidine B associates to form both n-mers and larger aggregates. n was found to depend on temperature, with n = 8 at 20° and 25°.