REGULATION OF THE ILVY AND ILVC GENES IN ESCHERICHIA COLI K-12
Abstract
I have conducted studies to explore the structure and regulation of the ilvY and ilvC genes in Escherichia coli K-12. Previous studies have shown that the ilvY gene encodes a positive regulatory protein, upsilon, that is required for the expression of the adjacent ilvC gene. My analysis of ilvY expression in vitro demonstrated that the gene is autogenously regulated. This control appears to be at the level of translation since no autogenous control of ilvY transcription was observed in vivo. The nucleotide sequence of the ilvY-ilvC region was determined which allowed me to localize the ilvA terminator, the ilvY gene, and the beginning of the ilvC gene. The ilvY and ilvC genes are expressed from divergent overlapping promoters. Furthermore, the distal portions of the ilvY and ilvA genes appear to overlap in an anti-parallel manner. Analysis of my sequence has revealed a repetitive sequence which we believe encodes a binding site for the upsilon protein. I have also determined the nature of the constitutive ilvY mutation by sequence analysis. The mutation is due to a single base change located in the middle of the ilvY gene. In the course of my study we discovered a transcript within the ilvY region that is directed in the opposite orientation from the ilvY gene. The promoter for this transcript was localized to the area proximal to the ilvC gene. Thus, I suggest that this transcript may serve as a basal level ilvC promoter. This transcript may also be responsible for inducer independent expression of ilvC that was observed upon growth at 30(DEGREES)C.
Degree
Ph.D.
Subject Area
Molecular biology
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.