regulatory proteins that affect transcription Flashcards
E. coli prefers to catabolize ___ not ____
glucose not lactose, will not use both at the same time
at a very low level E. coli will synthesize
the proteins required for the catabolism of lactose unless there is no glucose but some lactose present
lac operon and lacI
are regulatory proteins that affect transcription
LacI fn and where is it
repressor, not part of operon
LacZ fn an where is it
hydrolyzes lactose into monoers that can be catabolized by glycoysis, part of operon and in PM
LacY
lactose permease, part of operon. Allows for uptake of lactose across PM
CAP
an activaotr protein that can bind to a site upstream of promotor called an activator binding site, in lac operonactivator is called CAP
fn of CAP
help RNA pol bind to promoter and begin transcription. however CAP will only bind to the activator binding site if it has first bound to cyclic AMP
what is cAMP
regulatory nucleotide. when synthesized cAMP can bind to CAP. CAP-cAMP can bind to activator binding site (ABS), helps RNA pol bind to promotor and begin transcription
LacI
not part of operon, always synthesized, is a repressor meaning binds to regions of DNA called the operator. the operator is downstream of the promoter
what happens is LacI is bound to operator
prevent RNA pol from binding to promoter, inhibits transcrrption
what happens if lactose is present in cell’s cytoplasm
bind to LacI and prevent it from binding to the operator
if there is absecne of glucose then
cAMP will be synthesized and bind to CAP. CAP will bind to activator binindg site helping RNA pol bind
if there is presence lactose then
lactose bind to LacI. LacI will not bind to operator and inhibit binding of RNA pol
