Gene Regulation in Bacteria

Gene Regulation

The control of the timing and amount of gene expression in cells.

Constitutive Genes

Genes that are continuously expressed at constant levels, necessary for basic cellular functions.

Regulatory Proteins

Proteins that influence the initiation rate of transcription, containing DNA binding and allosteric sites.

Negative Control

A mechanism where a repressor protein inhibits gene expression.

Positive Control

A mechanism where an activator protein increases gene expression.

Inducible Control

A type of regulation where transcription is normally off but can be turned on by an inducer.

Repressible Control

A type of regulation where transcription is normally on but can be turned off by a corepressor.

Operon

A functional unit of DNA containing a cluster of genes regulated by a single promoter.

Polycistronic mRNA

mRNA that codes for multiple proteins from a single operon.

Promoter

The nucleotide sequence that initiates transcription of a gene.

Terminator

A nucleotide sequence that signals the end of transcription.

Lac Operon

A negative inducible operon involved in lactose metabolism regulated by the presence of lactose.

Lactose Permease

A membrane protein that facilitates the transport of lactose into the cell.

β-galactosidase

An enzyme that cleaves lactose into glucose and galactose.

Lac Repressor

A protein that inhibits the transcription of the lac operon when lactose is absent.

Allolactose

An effector molecule that binds to the lac repressor, preventing it from inhibiting the lac operon.

Catabolite Repression

A regulatory mechanism that reduces the expression of operons when preferred energy sources are available.

Trp Operon

A negative repressible operon that encodes enzymes for tryptophan biosynthesis.

Attenuation

A regulatory mechanism that causes premature termination of transcription in response to specific conditions.

Translational Repressors

Proteins that prevent the initiation of translation by blocking ribosomal access to mRNA.

Antisense RNA

RNA molecules that are complementary to mRNA and inhibit its translation.

Feedback Inhibition

A regulatory mechanism where the end product of a pathway inhibits its own synthesis by inhibiting an enzyme.

Posttranslational Modification

Chemical modifications of proteins after translation that can affect their function.

Riboswitch

RNA elements that can change structure in response to small molecule binding, influencing gene expression.

Effector Molecules

Small molecules that influence the activity of regulatory proteins either by aiding or inhibiting their action.

Corepressor

A substance that binds to a repressor protein and activates it to bind to DNA, inhibiting transcription.

Inducer

An effector molecule that binds to a repressor, inhibiting its ability to suppress transcription.

CAP Site

A binding site for the catabolite activator protein (CAP) within the lac operon.

Operator Region

A segment of DNA that a repressor protein binds to, blocking RNA polymerase from transcribing.

Leader Peptide

A small peptide encoded by the trpL gene that regulates the trp operon through attenuation.

Low Osmolarity

Conditions under which specific genes like OmpF are expressed in E. coli.

High Osmolarity

Conditions that trigger the expression of micF in E. coli, inhibiting translation of certain mRNAs.