Transfer RNA content and dissociability of mouse liver monosomes produced by histidinol

Biosynthesis, Quantification and Genetic Diseases of the Smallest Signaling Thiol Metabolite: Hydrogen Sulfide

Hydrogen sulfide (H₂S) is a gasotransmitter and the smallest signaling thiol metabolite with important roles in human health. The turnover of H₂S in humans is mainly governed by enzymes of sulfur amino acid metabolism and also by the microbiome. As is the case with other small signaling molecules, disease-promoting effects of H₂S largely depend on its concentration and compartmentalization. Genetic defects that impair the biogenesis and catabolism of H₂S have been described; however, a gap in knowledge remains concerning physiological steady-state concentrations of H₂S and their direct clinical implications. The small size and considerable reactivity of H₂S renders its quantification in biological samples an experimental challenge. A compilation of methods currently employed to quantify H₂S in biological specimens is provided in this review. Substantial discrepancy exists in the concentrations of H₂S determined by different techniques. Available methodologies permit end-point measurement of H₂S concentration, yet no definitive protocol exists for the continuous, real-time measurement of H₂S produced by its enzymatic sources. We present a summary of available animal models, monogenic diseases that impair H₂S metabolism in humans including structure-function relationships of pathogenic mutations, and discuss possible approaches to overcome current limitations of study.

Control of protein synthesis in mammalian cells by aminoacylation of transfer ribonucleic acid

The dependence of protein synthesis on the intracellular content of aminoacylated tRNA has been studied in mouse ascites tumor cells deprived for various amino acids. A remarkable reduction in net protein synthesis has been found only after a drastic decrease in aminoacylation of tRNA. The quantitative correlation of protein synthesis with the degree of aminoacylation suggests that a moderate amino acid starvation primarily influences the rate of elongation at the codon concerned. These results are in contrast to the findings previously reported for HeLa cells. Some crucial steps during the determination of intracellular aminoacyl-tRNA have been investigated. The reliability of the method employed has been discussed on a theoretical basis.