Theme 3 - Mod 1 - Modulating Transcription

What is needed for prokaryotic growth

A nutrient rich environment containing amino acids, carbohydrates, vitamins and nucleotides

Favourable temperature

Housekeeping genes

Constitutively expressed

Always being Transcribed and translated

Constant maintenance of general cellular activities

Includes structural and ribosomal proteins

Regulated genes

Expressed only when needed and includes enzymes

What is the glucose effect

It is the product of glucose metabolism itself that activates the switch between glucose and lactose use

B-Galactosidase

Can metabolize lactose to produce glucose and galactose

Produced by turning on transcription of the B-Galactosidase gene : Cell will only do this when no glucose is available

What did Francois Jacob and Jacques Manod do and how

Investigated how E.coli are able to produce B-galactosidase

Grew E.coli in a lactose free medium and the then removed it and at the same time measured the amount of B-galactosidase produced

What did they find

When lactose was added, the enzyme would increase and when it was removed the production of the enzyme was ceased

The production of B-galactosidase is dependent upon the presence of lactose in the environment

Transcriptional control

Controls amount of mRNA that is produced in the cell by controlling the binding of proteins to the promoter

Often prevalent with more drastic changes to the environment

eg. E.coli regulating amount of B-galactosidase transcribed

Translational control

The rate at which translation occurs will affect the amount of protein produced

Post-translational control

Regulate the ability of the protein to become active or inactive by driving the assembly into complexes, the binding of substrates or the unmasking of enzymatic domains

What level of regulation is the fastest and why

Post-translational

Holds a bunch of inactive proteins and can become active when given appropriate signal by the environment

What level of regulation is the slowest and why

Transcriptional

Cell is starting from scratch

Expression of a functional protein requires transcription, translation and modification

What level of regulation is the most efficient and why

Transcriptional

Doesn't waste energy or resources in making mRNA or a polypeptide

Most economical