MICRB316 Lecture 16: Lecture 16.doc
8 Mar 2014
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Document Summary
Defines a network of positive & negative tn regulation. Involves a large number of metabolic & biosynthetic operons. >70 different genes under control of lrp aa met/biosyn operons; nutrient transport; fimbriae synth. Generally, biosynthetic pathways are positively affected; catabolic pathways are repressed by lrp. L-leucine is most important effector for some pathways. But (exceptionally) there is no unifying stimulus for the lrp regulon. Lrp induces synthesis of biosynthetic genes needed in poor medium & represses. Tn of proteins needed for growth in rich medium. In rich medium, the amount of lrp is at its lowest in the cell. Biosynthesis genes are activated, catabolic genes are repressed. Lrp is an activator or repressor; its unique in sequence it has no homology to other regulators; 163 aas; 19 kda; basic charge; active form = dimer; 300 copies/cell. Copy number is maximal at log phase & dependent on quality of growth medium.
