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Title: A characterisation of two genes of Escherichia coli, and the possible effect of BIMEs on gene expression
Author: Wedgwood, Stephen
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1996
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In the course of work aimed at discovering genes encoding novel sigma subunits of Escherichia coli RNA polymerase, two unknown open reading frames were identified by hybridisation of an E. coli genome library with synthetic oligonucleotide probes directed against the conserved subregion 2.1 of bacterial sigma factors. This thesis describes the mapping, sequencing, and characterisation of these genes. The open reading frame f229 was located near 4324kb on the physical map of the E. coli K12 chromosome. Its sequence and that of a downstream Bacterial Interspersed Mosaic Element (BIME) were determined. Transcription of f229 was not detectable under normal growth conditions, nor was it found to be inducible by various environmental shocks. However, f229 mRNA levels increased dramatically following alteration of the BIME structure, either by complete removal or by a deletion leaving just a single Palindromic Unit. A protein encoded by f229 was identified and had the expected molecular size of 25kDa, but was found to be poorly expressed even in the absence of the BIME. Moreover, an f229::kanR mutation did not affect growth of E. coli under a variety of conditions. Since the predicted amino acid sequence of F229 has no identify with any known protein and no similarity to members of either of the two known sigma families, the function of f229 remains unknown. The downstream portion of a second open reading frame was located near 381kb on the physical map. The amino acid sequence has very high identity (80% range) with a family of Pseudomonas enzymes, the 4-hydroxy-2-oxovalerate aldolases. These participate in a metabolic pathway that converts a variety of aromatic compounds into Krebs Cycle intermediates. Since E. coli is known to carry out similar catabolic reactions and the corresponding genes in Pseudomonas are clustered into operons, it is likely that the unsequenced region upstream of this open reading frame contains further genes involved in aromatic degradation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available