BIOL 331 Lecture Notes - Lecture 11: Ribosomal Rna, Conformational Change, Inverted Repeat
23 Feb 2015
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House keeping genes: needed all the time. Regulated genes: not turned on all the time. 4000 genes in e. coli genome, they need certain genes turned, don"t want to turn on lots of genes at high levels and end up wasting a lot of energy. Instead can express at a very low level (basal), and make trace amounts. Can divided activation into 2 different mechanisms: rna polymerase recruitment, allosteric activation, rna polymerase recruitment. Promoters for these genes are very poor, rna polymerase can bind to promoter, but cannot stably anneal with promoter, so it will fall off so don"t get any transcription. These genes are turned on by use of activators, which have an activator binding site, which is always located upstream of promoter site. Have protein-protein interactions between activator and alpha-subunit of rna polymerase to position rna polymerase in promoter region. Rna polymerase doesn"t recognize promoter very well, activator helps recruit it.
