Chapter 14: Regulation of Cellular Processes

Vocabulary practice flashcards covering bacterial gene expression, operon regulation, global regulatory systems, and cellular responses based on Prescott's Microbiology, 12th Edition.

Constitutive genes

Also known as housekeeping genes, these encode enzymes of the central metabolic pathway and provide the cell with a constant supply of active enzymes.

Inducer

A small effector molecule that stimulates gene expression; required for inducible genes only when their substrate is available.

Corepressor

A small effector molecule that works with repressible genes, which are usually involved in biosynthetic pathways and are present unless the end product is available.

Transcription factors

Regulatory proteins containing a DNA binding domain, such as a helix-turn-helix, that interact with the promoter or effector molecules to control transcription initiation.

Negative transcriptional control

A regulatory mechanism where a repressor protein binds to the operator to inhibit transcription initiation by blocking RNA polymerase.

Positive transcriptional control

A regulatory mechanism where an activator protein binds to activator binding sites upstream of the promoter to encourage RNA polymerase binding.

Operon

A unit consisting of structural genes together with the upstream regulatory region; often considered leaky with a low, basal level of transcription.

$$\beta\text{-galactosidase}$$

An enzyme that hydrolyzes lactose into galactose and glucose; its levels increase from $3$ to $3,000$ molecules per cell in the presence of lactose.

Allolactose

The inducer molecule in the lac operon system produced by $\beta\text{-galactosidase}$ that binds to the lac repressor, preventing it from binding to the operator.

Attenuation

A type of regulation that controls transcription termination within the leader region of mRNA, first demonstrated in the E. coli trp operon.

Riboswitches

Folding patterns in the RNA leader sequence that determine if transcription will continue or terminate based on the binding of effector molecules.

T box riboswitch

A riboswitch where the binding of uncharged tRNA prevents transcription termination to lead to gene expression for amino acid biosynthesis.

RNA thermometers

RNA secondary structures in the leader sequences of mRNAs, often AU-rich, that change in response to temperature to activate gene expression.

Antisense RNAs

Small noncoding RNA molecules (sRNAs) complementary to mRNA that function by base pairing to inhibit or enhance translation.

Regulon

A collection of genes or operons controlled by a common global regulatory protein.

Sensor kinase

A protein in a two-component signal transduction system that spans the plasma membrane, phosphorylates itself, and transfers the phosphate to a response regulator.

Alternate sigma factors

Proteins that direct RNA polymerase to specific subsets of bacterial promoters to immediately change the expression of many genes, such as $\sigma^{32}$ for heat shock.

Second messengers

Small molecules like $cAMP$, $ppGpp$, or $c\text{-di-GMP}$ produced in response to an external signal that redirect cellular physiology and gene expression.

Diauxic growth

A biphasic growth pattern where a cell preferentially uses one carbon source before exhausting it and switching to a second source after a lag phase.

Catabolite Activator Protein (CAP)

Also called cyclic AMP receptor protein (CRP), it is active when bound to $cAMP$ and stabilizes the interaction of RNA polymerase with promoters of catabolite operons.

Stringent response

A global mechanism to slow growth in response to nutritional stress, involving the production of alarmones like $(p)ppGpp$ by the protein RelA.

Methyl-accepting chemotaxis proteins (MCPs)

Chemoreceptors in the E. coli membrane that bind environmental chemicals and initiate signaling through CheA and CheY to control flagellar rotation.

Quorum sensing

Cell-to-cell communication mediated by small signaling molecules like N-acylhomoserine lactone (AHL) to coordinate gene expression based on cell density.

CRISPR/Cas system

An adaptive immunity system in bacteria involving adaptation, expression, and interference stages to respond to and protect against bacteriophage infection.