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EF-Tu and RNase E :
EF-Tu and RNase E : Essential and Functionally Connected Proteins
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- Hammarlöf, Disa L., 1980- (författare)
- Uppsala universitet,Mikrobiologi
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- Hughes, Diarmaid, Professor (preses)
- Uppsala universitet,Institutionen för medicinsk biokemi och mikrobiologi
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- Ehrenberg, Måns, Professor (preses)
- Uppsala universitet,Struktur- och molekylärbiologi
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- Wagner, Gerhart, Professor (preses)
- Uppsala universitet,Mikrobiologi
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- Buckingham, Richard H, Emeritus C.N.R.S. Director of Research (opponent)
- Institut de Biologie Physico-Chimique
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(creator_code:org_t)
- ISBN 9789155481797
- Uppsala : Acta Universitatis Upsaliensis, 2011
- Engelska 49 s.
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Serie: Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1651-6214 ; 863
- Relaterad länk:
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https://uu.diva-port... (primary) (Raw object)
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https://urn.kb.se/re...
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Abstract
Ämnesord
Stäng
- The rate and accuracy of protein production is the main determinant of bacterial growth. Elongation Factor Tu (EF-Tu) provides the ribosome with aminoacylated tRNAs, and is central for its activity. In Salmonella enterica serovar Typhimurium, EF-Tu is encoded by the genes tufA and tufB. A bacterial cell depending on tufA499-encoded EF-Tu mutant Gln125Arg grows extremely slowly. We found evidence that this is caused by excessive degradation of mRNA, which is suggested to be the result of transcription-translation decoupling because the leading ribosome is ‘starved’ for amino acids and stalls on the nascent mRNA, which is thus exposed to Riboendonuclease RNase E. The slow-growth phenotype can be reversed by mutations in RNase E that reduce the activity of this enzyme. We found that the EF-Tu mutant has increased levels of ppGpp during exponential growth in rich medium. ppGpp is usually produced during starvation, and we propose that Salmonella, depending on mutant EF-Tu, incorrectly senses the resulting situation with ribosomes ‘starving’ for amino acids as a real starvation condition. Thus, RelA produces ppGpp which redirects gene expression from synthesis of ribosomes and favours synthesis of building blocks such as amino acids. When ppGpp levels are reduced, either by over-expression of SpoT or by inactivation of relA, growth of the mutant is improved. We suggest this is because the cell stays in a fast-growth mode. RNase E mutants with a conditionally lethal temperature-sensitive (ts) phenotype were used to address the long-debated question of the essential role of RNase E. Suppressor mutations of the ts phenotype were selected and identified, both in RNase E as well as in extragenic loci. The internal mutations restore the wild-type RNase E function to various degrees, but no single defect was identified that alone could account for the ts phenotype. In contrast, identifying three different classes of extragenic suppressors lead us to suggest that the essential role of RNaseIE is to degrade mRNA. One possibility to explain the importance of this function is that in the absence of mRNA degradation by RNase E, the ribosomes become trapped on defective mRNAs, with detrimental consequences for continued cell growth.
Ämnesord
- NATURVETENSKAP -- Biologi -- Mikrobiologi (hsv//swe)
- NATURAL SCIENCES -- Biological Sciences -- Microbiology (hsv//eng)
Nyckelord
- bacterial growth
- translation
- EF-Tu
- RNase E
- mRNA
- RNA degradation
- Molekylär cellbiologi
- Molecular Cellbiology
- Mikrobiologi
- Microbiology
Publikations- och innehållstyp
- vet (ämneskategori)
- dok (ämneskategori)
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