Nathan Brot

Role of GTP in protein synthesis: Interaction of GTP with soluble transfer factors from E. coli

Abstract Using partially purified preparations of the soluble transfer factors Ts and Tu from E. coli it has been possible to study the kinetics of the formation of a GTP-protein complex. The data show that Ts affects the rate of complex formation and that Tu determines the amount, or extent, of the GTP complex. In addition, two protein factors that possess Ts activity have been separated by Sephadex G-100 chromatography. One of these (Ts1) exhibits a different Chromatographic pattern on Sephadex G-100 in the presence of GTP.

The formation of a complex containing ribosomes, transfer factor G and A guanosine nucleotide

Abstract Several guanosine nucleotides stimulate the binding of transfer factor G to E. coli ribosomes. A binding of these nucleotides to the ribosome-factor G complex has also been demonstrated.

Studies on the nature of the bound cobamide in E. coli N5-methyltetrahydrofolate-homocysteine transmethylase

Abstract N 5 -methyl-H 4 -folate-homocysteine transmethylase, purified 100-fold from E. coli , was studied with respect to the content and the chemical nature of its cobamide prosthetic group. Extraction of the enzyme with hot ethanol in the absence of alkaline cyanide removed 50% of the bound eobamide. A light-sensitive cobamide containing 5,6-dimethylbenzimidazole and exhibiting the spectrophotometric, Chromatographic, and electrophoretic characteristics of sulphito-B 12 was obtained. In addition, various cobamides protected the apoenzyme form of the enzyme from inactivation by parachloromercuribenzoate.

Conversion of l-tyrosine to phenol by Clostridium tetanomorphum

Abstract Clostridium tetanomorphum rapidly converst tyrosine-C 14 to phenol in whole cells and in cell-free extracts. An enzyme catalyzing the reaction was purified 90-fold from C. tetanomorphum and the characteristics of the reaction were examined.

Studies on the reaction of N-acetyl-phenylalanyl-tRNA with puromycin

Abstract The effect of poly U on the ribosome dependent reaction of N -acetyl-phe-tRNA with puromycin has been investigated using an extraction procedure to assay for the production of the puromycin peptide. At 20 or 30 m m Mg the formation of a puromycin product did not require poly U, but poly U stimulated the reaction at 10 m m Mg, and was required along with initiation factors and GTP at 6 m m Mg. At 20 m m Mg, the soluble transfer factor G and GTP stimulated the reaction 3-fold, but only in the presence of poly U.

Studies on the participation of the enzyme-bound cobamide in transmethylation from N5-methyl-H4-folate and methyl-B12

Abstract The role of the cobamide prosthetic group of N5-methyl-H4-folate-homocysteine methyl transferase in 3 methyl transferase reactions catalyzed by this enzyme has been examined. Propylation of the cobamide prosthetic group inhibits methyl transfer from N5-methyl-folate-H4, but not from methyl-B12. These results offer evidence that methyl transfer from N5-methyl-H4-folate involves the cobamide site on the enzyme, while methyl transfer from methyl-B12 utilizes a different catalytic site.