Ribosome Reassembly in Salmonella Typhimurium During Recovery From Sublethal Heat Injury
Genthner, Fred John
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https://hdl.handle.net/2142/70073
Description
Title
Ribosome Reassembly in Salmonella Typhimurium During Recovery From Sublethal Heat Injury
Author(s)
Genthner, Fred John
Issue Date
1983
Department of Study
Food Science
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Microbiology
Abstract
Sublethal heat injury of Salmonella typhimurium at 48 C for 60 min in potassium phosphate buffer, pH 7.2, containing 50 mM ethylene-diaminetetraacetic acid (EDTA) caused degradation of the 16S ribosomal (r)RNA and the disruption of the 30S subunit. The damaged ribosomes were found on sucrose gradients as 70S aggregates formed by the nonspecific binding of 30S r-proteins to the largely intact 50S subunits. The 50S ribosomal subunit protein L25 and at least nine 30S r-proteins were found to be present in reduced amounts on this structure.
S. typhimurium 23S rRNA was shown to be an aggregate of smaller rRNA species. It was separated by polyacrylamide and formamide gel electrophoresis into four species having molecular masses of 0.90, 0.66, 0.39, and 0.20 x 10('6) daltons.
Pulse-labeling experiments, using normal and recovering cells, showed that these smaller rRNA polynucleotides were not derived from a 23S rRNA precursor. In addition, four ribonucleoprotein particles (48S, 43S, 36S, and 30S) were isolated from repairing cells by sedimentation through sucrose gradients.
Puromycin inhibited the ribosome assembly process in S. typhimurium during the later stages of recovery following heat injury. Sucrose gradient and polyacrylamide gel electrophoresis showed that both subunits and the 16S rRNA failed to mature.
Ribosomal proteins S14, S20/L26, S21, and L32/33 were present in reduced amounts in the heat injured cell. Thus, the failure of the entire preheat complement of ribosomal subunits to fully mature during recovery in the presence of puromycin may be due, in part, to limiting amounts of these r-proteins in the heat injured cells.
Other quantitative and qualitative determinations of r-proteins under various experimental conditions revealed that those r-proteins which did not remain bound to the heat damaged ribosome did not participate in ribosome reassembly in cells recovering in either the presence or absence of puromycin. Instead, r-proteins which were preferrentially synthesized during recovery competed more successfully for incorporation into the reassembled subunits that did the unbound, preheat r-proteins. Only those preheat r-proteins which remained bound to the damaged ribosome were able to participate in ribosome reassembly.
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