Regulation II

26 important questions on Regulation II

What are the main advantages of regulating protein activity?

It is reversible and it has a fast/immediate adaptation to changes in metabolic conditions

What two mechanisms are there for regulating protein activity?

Feedback inhibition and post-translational modification

What is feedback inhibition?

A major way of controlling protein activity, that temporarily turns off the reactions in an entire pathway
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How is feedback inhibition controlled?

The end-product of the pathway, which inhibits an early enzyme of the pathway

What two binding sites does the inhibited enzyme have?

An active site for substrate binding and an allosteric site for end-product binding

What is covalent modification?

The attachment or removal of a small molecule to or from the enzyme

What do signal transduction systems allow?

The cell to react to an external stimulus and link events outside of the cell with gene expression

What two components do signal transduction systems consist of?

A sensor kinase and a response regulator

What is a sensor kinase?

A transmembrane protein that in response to an environmental signal can phosphorylate itself

What is a response regulator?

A regulatory protein that accepts a phosphate group from the signal kinase and regulates transcription of specific genes

What does a bacteria need in order to utilize chemotaxis?

It needs to sense chemical gradient and have movement in a directed fashion (motility)

What are peritrichous flagella?

A type of flagellum that contains motors that all rotate in one direction

What happens if one of the peritrichous motors switches to clockwise rotation?

The flagella dissociate from the bundle and tumble the cell to face a new direction

What happens if the organism senses that it is moving toward a higher attractant concentration?

The runs become longer and tumbles less frequent

What are Methyl-accepting chemotaxis proteins (MCPs)?

Sensory proteins in the cytoplasmic membrane

What happens if a repellent binds to MCP?

CheA-P passes P to CheY, which binds to the flagellar motor and induces a tumble

What happens if an attractant binds to MCP?

CheY can‘t bind to flagellar motor the  flagellum continues to rotate counterclockwise and a run occurs

What is an example of covalent modification?

Methylation

What happens if MPC is methylated?

There is no response to attractants, but it is sensitive to repellents

What happens if MPC is unmethylated?

There is a strong response to attractants, but it is insensitive to repellents

What does methylation of MPC result in?

Increased phosphorylation activity of CheA, which results in more demethylation of MCPs and thus a reset of system

What is quorum sensing?

Coordination of gene expression in microbial populations that occurs through cell-to-cell communication

What are examples of coordinated activities in bacteria?

Biofilm formation, virulence, production of antibiotics, plasmid transfer and bioluminescence

What signal molecules are present in quorum sensing?

Autoinducers

What is the AHL sythase expression at low cell densities?

It is at a basal level and the levels outside the cell are low

What is the AHL synthase expression at high cell densities?

The AHL outside the cell is high so they diffuse in the cell and activate the transcription of specific genes for AHL synthase

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