Dept. of Biological Sciences
Undergraduate Office
Biochemistry, Molecular Biology, Biochemical Genetics
Growth of an organism depends upon achieving an optimal balance among the various cellular processes.
It is estimated that
the bacteria Escherichia coli K-12 converts as much as 10% of the
glucose utilized for its growth to the amino acids isoleucine,
leucine and valine. Thus, the synthesis of these three amino
acids represents a substantial investment of cellular resources,
and therefore presumably their biosynthesis is tightly regulated.
Because these three amino acids share a common biochemical pathway,
the cell utilizes both genetic and biochemical regulation to
achieve the necessary balance among these amino acids. The genes
for the enzymes are divided into five clusters each regulated by
different signals. Also, specific enzymes are allosterically affected
by an individual amino acid to modulate the flow of intermediates
through the pathway. Our research group studies the
ilvGMEDA operon the largest of the gene clusters. Currently, our
efforts are to assess both the transcriptional effectors of these
genes and the structural elements of the enzyme threonine deaminase
that result in its allosteric regulation by isoleucine
feedback inhibition.
Selected Publications:
Lopes, J.M. and R.P. Lawther. 1989. Physical identification of
an internal promoter, ilvAp, in the distal portion of the ilvGMEDA operon.
Gene 76:255-269.
Lopes, J.M., N. Soliman, P.K. Smith, and R.P. Lawther. 1989.
Transcriptional polarity enhances the contribution of the internal promoter,
ilvEp, in the expression of the ilvGMEDA operon in
wild type Escherichia coli K-12. Molec. Microbiol. 3:1039-1051.
Lawther, R.P., J.M. Lopes, M.J. Ortuno, and M.C. White. 1990.
Analysis of the regulation of the ilvGMEDA operon using leader-
attenuator-galK gene fusions. J. Bacteriol. 172:2320-2327.
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