Gene Regulation in Bacteria

Flashcards about Gene Regulation in Bacteria

Gene regulation

The level of gene expression can vary under different conditions.

Constitutive genes

Genes that are unregulated with constant levels of expression; code proteins continuously necessary for survival.

Regulatory transcription factors (RTFs)

Proteins that increase or decrease the rate of RNA synthesis.

Inducible genes

Genes that can have gene transcription increased with inducers.

Repressible genes

Genes that can have gene transcription decreased.

Inducers

Small effector molecules that increase gene transcription by binding to activators or preventing repressors from binding to DNA.

Corepressors

Small effector molecules that decrease gene transcription by binding to repressors.

Inhibitors

Small effector molecules that decrease gene transcription by binding to activators.

Enzyme adaptation

A particular enzyme appears in the cell only after the cell has been exposed to the enzyme’s substrate

Operon

A regulatory unit consisting of a few protein-coding genes under the control of one promoter.

Polycistronic mRNA

mRNA that contains the coding sequence for two or more protein-coding genes.

lacZ

Codes β-galactosidase, which cleaves lactose and converts it to allolactose.

lacY

Codes lactose permease, a membrane protein required for lactose transport.

lacA

Codes galactoside transacetylase, which modifies lactose and prevents toxic buildup of nonmetabolizable lactose analogs.

lacI gene

Codes lac repressor (functions as a tetramer) and is constitutively expressed.

Allosteric regulation

Allolactose binds to lac repressor and inactivates it.

Catabolite repression

E. coli uses glucose first, preventing the use of lactose.

Diauxic growth

The sequential use of two sugars by a bacterium.

cAMP

A small molecule produced from ATP that binds to the Catabolite Activator Protein (CAP).

Catabolite Activator Protein (CAP)

An activator protein that binds cAMP; the cAMP-CAP complex increases transcription.

trp operon

Involved in the biosynthesis of tryptophan.

trpR

Codes the trp repressor protein.

trpL

Codes a short peptide called the leader peptide; functions in attenuation.

Feedback inhibition

The product of a metabolic pathway inhibits the first enzyme in the pathway.

Allosteric enzyme

An enzyme with a catalytic site (binds substrate) and a regulatory site (binds final product).