Effects of protein overexpression on Escherichia coli physiology /
The goal of this study was to investigate elects of protein overexpression on the physiology of Escherichia coli. Effects of protein overexpression can be divided into two aspects, the general effect common to all protein overexpression and the specific effects particular to the biochemical activity...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731685611&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The goal of this study was to investigate elects of protein overexpression on the physiology of Escherichia coli. Effects of protein overexpression can be divided into two aspects, the general effect common to all protein overexpression and the specific effects particular to the biochemical activity of the protein overexpressed. The general elect was investigated by overexpressing an inactive protein LuxA (the α subunit of luciferase). Results led to the following model. When a gene is overexpressed, its elevated transcripts bind to a large number of ribosomes. The rest of the mRNA pool has to compete for the reduced number of gee ribosomes. Therefore, some of the genes involved in essential metabolism are down-regulated, leading to reduced growth rate. The reduced growth rate is then sensed by the growth rate control mechanism, which reduces the rate of rRNA synthesis. Protein overexpression also leads to the destruction of ribosomes (18). The reduced rate of rRNA synthesis and increased degradation rate result in a reduced ribosome number, which further intensifies the competition for free ribosomes. The effect of phosphoenolpyruvate carboxykinase (Pck) overexpression was characterized as an example of the specific effect of protein production. Pck overexpression retards growth more than the overexpressional non-functional protein, LuxA, possibly accuse the increased enzymatic activity perturbs the metabolite pools, which in turn upset global regulation. In particular, we bound that Pck overexpression abolishes the induction of glnA transcription under nitrogen limitation in a strain deficient in phosphotransacetylase, which is responsible for the reversible inter-conversion of acetyl coenzyme A and acetyl phosphate. This effect was not observed when a Pck mutant, Pck51, which has a new oxaloacetate decarboxylase activity, was overexpressed. Therefore, the specific elect of overexpressing Pck is attributable to the PEP-formation activity of Pck. |
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| Item Description: | Vita. "Major Subject: Chemical Engineering". |
| Physical Description: | x, 105 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 93-102). |