Workshop IV Flashcards
What are the products of enzymatic hydrolysis of lactose?
What is the name of the enzyme used?
D-galactose & D-glucose
B-galactosidase
What is an operon?
All the genes transcribed into the same mRNA + any adjacent cis-acting sites involved in transcription or regulation.
What is a regulon?
Multiple operons under control of a single regulatory protein
What does lactose operon consist of?
- lacZ gene - B-galactosidase
- lacY gene - lactose permease
- lacA gene - galactoside transacetylase
- lacP - promoter of the operon
- lacO - operator site involved in transcriptional regulation
- lacI - repressor protein gene
- lacC - binding site for CRP dimer
What is the function of the CRP protein
Forms a dimeric protein with the help of cAMP and binds to C region on, stabilising the binding of RNA polymerase to the promoter.
What is the role of inducer and what can it be?
An inducer molecule binds to the cI repressor protein, preventing it from blocking the lac operon. e.g. allolactose
What is the structure and function of the repressor protein?
cI is a tetrameric protein to O2 and O3 or O1 and O3 on the operator region bending the DNA, which prevents the DNA polymerase from binding.
What happens in presence of glucose and absence of lactose?
Increased cI expression, decreased cAMP conc –> CRP protein cant bind the DNA –> RNA polymerase cannot be stabilised on the DNA.
What happens in presence of glucose and lactose?
small amount of lactose is converted to allolactose(inducer) inactivating the inhibitng protein, but since a better sugar source is available there is a low level of transcription on lac operon.
What happens in absence of glucose and presence of lactose?
small amount of lactose is converted to allolactose(inducer) inactivating the inhibitng protein, lac operon is intensively transcribed.
