Chapter 15- Regulation of Gene expression. Regulation is important! Regulation makes sense - the bacteria/cell does the logical, intelligent thing- so you can ask “what would I do if I were a microbe?”, and usually you’ll be right. Lots of wood (fuels)/brick analogies, and stories.
OPERON: coordinately regulated genes, usually on the same mRNA in bacteria.
TWO conditions needed to utilize lactose: 1) lactose has to be there; 2) glucose has to be absent- again, it makes sense!
Control system: fig 15-1-7: This is the situation when no glucose is present, and lactose induces the operon. Please study these figures!!!!
Lactose (actually, allolactose- is really much smaller Allostearic interaction
Repressor acts negatively to inhibit transcription.
Proof: isolation and behavior of constitutive mutants, such as Oc and lacI-, and dominance/recessive behavior as merodiploids. Table 15.1 Also biochemistry- isolation of repressor protein, binding characteristics to operator, etc.
However, good repressor will work, so an I-/I+ merodiploid will be regulated.
A good operator will NOT work to restore regulation!!
A superrepressor (Is) will bind, shutting off transcription, no matter what- it will be dominant over an I+
CAP is kind of like a transcription factor- + acting, stimulating transcription
CAP regulates probably 50 genes- NO sugar or other carbon source would be used, as long as glucose is there!
MORE allosteric interaction!
What do transcription factors really look like?
There are recurring patterns, called motifs – the beta barrel is one of those others…
Here’s a very simple eukaryotic regulation path. Steroids, unlike other hormones, take a long time to work an do so by affecting transcription. The hormone-receptor scale is WAY off.
Ways to make multiple proteins form the same gene
Just to amaze you…