Biomaterial Database

The site of ribosome degradation in starved Escherichia coli cells. 1976

R Kaplan, and E Hartstein

An attempt was made, in starved Escherichia coli cells, to locate the site at which the process of ribosome degradation is initiated. Supernatant and rapidly sedimenting pellet fractions from exponentially growing and from carbon-starved cells were prepared, and the ribonucleic acids from these fractions were seperated by polyacrylamide electrophoresis and quantitated. The data indicated that 23 S, 16 S, and 5 S RNA are lost only from the pellet; and also that the low molecular weight RNA degradation products are confined to this fraction. Ribosomes from supernatant and pellet fractions were seperated on sucrose density gradients. The sedimentation profiles obtained indicated that pellet fractions of starved cells contain for the most part 50 S and 30 S subunits, whereas 70 S monosomes were most abundant in the supernatant fraction. In vitro measurements on RNA degradation in supernatant and rapidly sedimenting pellet fractions confirmed the in vivo data on the exclusive degradation of ribosomal RNA in the pellet. Based on these data and on previous observations, we suggest that the endoribonucleolytic attack which triggers ribosome degradation, occurs in free subunits attached to the rapidly sedimenting membrane fraction. Subsequently, the ribosome falls apart, and the small RNA pieces generated remain attached to the pellet fraction until their final degradation by the exonuclease.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D002244	Carbon	A nonmetallic element with atomic symbol C, atomic number 6, and atomic weight [12.0096; 12.0116]. It may occur as several different allotropes including DIAMOND; CHARCOAL; and GRAPHITE; and as SOOT from incompletely burned fuel.	Carbon-12,Vitreous Carbon,Carbon 12,Carbon, Vitreous
D002458	Cell Fractionation	Techniques to partition various components of the cell into SUBCELLULAR FRACTIONS.	Cell Fractionations,Fractionation, Cell,Fractionations, Cell
D002499	Centrifugation, Density Gradient	Separation of particles according to density by employing a gradient of varying densities. At equilibrium each particle settles in the gradient at a point equal to its density. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Centrifugations, Density Gradient,Density Gradient Centrifugation,Density Gradient Centrifugations,Gradient Centrifugation, Density,Gradient Centrifugations, Density
D004591	Electrophoresis, Polyacrylamide Gel	Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.	Polyacrylamide Gel Electrophoresis,SDS-PAGE,Sodium Dodecyl Sulfate-PAGE,Gel Electrophoresis, Polyacrylamide,SDS PAGE,Sodium Dodecyl Sulfate PAGE,Sodium Dodecyl Sulfate-PAGEs
D004926	Escherichia coli	A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.	Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D012270	Ribosomes	Multicomponent ribonucleoprotein structures found in the CYTOPLASM of all cells, and in MITOCHONDRIA, and PLASTIDS. They function in PROTEIN BIOSYNTHESIS via GENETIC TRANSLATION.	Ribosome
D012335	RNA, Ribosomal	The most abundant form of RNA. Together with proteins, it forms the ribosomes, playing a structural role and also a role in ribosomal binding of mRNA and tRNAs. Individual chains are conventionally designated by their sedimentation coefficients. In eukaryotes, four large chains exist, synthesized in the nucleolus and constituting about 50% of the ribosome. (Dorland, 28th ed)	Ribosomal RNA,15S RNA,RNA, 15S