Molecular Regulation Practice Flashcards

Flashcards covering molecular regulation concepts including quorum sensing, transcriptional control mechanisms (repressors/activators), and the E. coli lactose operon.

Aliivibrio fischeri

The bacteria living within the Hawaiian Bobtailed Squid that produce light.

Quorum Sensing

A process requiring the accumulation of a secreted small molecule (autoinducer) that, at a certain extracellular concentration, reenters cells and binds to a regulatory molecule to activate transcription.

Autoinducer (AI)

A secreted small molecule, such as acyl homoserine lactone, that triggers quorum sensing when it reaches a threshold concentration.

LuxR

The regulatory molecule in Alliivibrio fischeri that, when bound to an autoinducer, activates the transcription of luciferase.

LuxI

The protein responsible for synthesizing the acyl homoserine lactone autoinducer.

Luciferase

The enzyme that produces bioluminescence through the reaction: $FMNH_2 + O_2 + RCHO \rightarrow FMN + RCOOH + H_2O + \text{Light}$.

Repressors

Regulatory proteins that bind to specific DNA sequences to prevent the transcription of target genes.

Inducer

A ligand that binds to a repressor to release it from the DNA, allowing transcription to occur.

Induction

The continued expression of a target gene that occurs when an inducer causes a repressor to release from the DNA.

Corepressors

Ligands that must bind to certain repressors to enable them to bind to regulatory sequences.

Derepression

The process where a repressor releases from DNA because its corepressor ligand has disappeared from the cell.

Activators

Regulatory proteins that bind to DNA sequences and touch RNA polymerases near promoters to stimulate transcription; most must first bind a small ligand.

Sensor kinases

Proteins in the cell membrane that bind to environmental signals and regulate cytoplasmic events via phosphorylation.

Response regulator

A cytoplasmic protein that takes a phosphate from a sensor kinase and binds the chromosome to alter the transcription rate of genes.

Jacques Monod and François Jacob

French scientists who, in 1961, proposed that genes in E. coli could be regulated.

Inducible Enzymes

Enzymes that are produced only when a specific substrate (like lactose) is added to the media.

Constitutive Enzymes

Enzymes that are produced all the time, such as those used to metabolize glucose in E. coli.

Lactose permease (LacY)

A membrane protein that uses proton motive force (PMF) to move lactose into the cell.

$\beta$-galactosidase (LacZ)

An enzyme that, at high levels, cleaves lactose into galactose and glucose, and at low levels, modifies the linkage of lactose to produce allolactose.

Allolactose

The inducer of the lac operon, produced by high-level rearrangement of lactose by $\beta$-galactosidase.

LacI

The repressor protein for the lacZYA operon; it constitutes its own transcriptional unit with its own promoter.

Diauxic growth

A growth pattern seen when two carbon sources are present where the operon for one nutrient is repressed by the presence of a more favorable nutrient.

Catabolite Repression

The mechanism by which a preferred carbon source (like glucose) represses the production of enzymes for other nutrients (like $\beta$-galactosidase).

Inducer Exclusion

The process where glucose transport into the cell inhibits lactose import via the inhibition of LacY (lactose permease) by unphosphorylated IIA Glc.