Brock Biology Of Microorganisms Chapter 8

Front 1

Feedback inhibition

Back 1

occurs primarily in the regulation of entire biosynthetic pathways like in the biosynthesis of amino acids or nucleotides

Front 2

Three characteristics of Feedback inhibition

Back 2

1) the end product can regulate its own biosynthesis

2) the end product can inhibit the acitivity of the 1st enzyme in the pathway

3) shuts down entire biosynthetic pathway

Front 3

Allostery

Back 3

property that makes possible the process of feedback inhibition

Front 4

Active site

Back 4

where the substrate binds in an allosteric enzyme

Front 5

Allosteric Site

Back 5

where the inhibitor (effector) reversibly binds in an allosteric enzyme

binding at this site changes the enzyme conformation

Front 6

Isozymes

Back 6

different proteins that catalyze the same reaction but are subject to different regulatory controls

example is DAHP isozymes in E. coli

Front 7

Covalent Modification of Enzymes

Back 7

a regulatory mechanism for changing the catalytic activity of an enzyme

can be reversibly modified most times

Glutamine Synthetase is example of this

Front 8

Glutamine Synthetase

Back 8

example of covalent modification

modified by addition of AMP (adenylation)

Front 9

Protein Splicing

Back 9

occurs when amino acid residues are removed from the protein itself

intein is removed (portion of the peptide that is removed)

Front 10

Intein

Back 10

portion of the peptide that is removed during protein splicing

are self splicing

Front 11

In what groups does protein splicing occur?

Back 11

occurs in Archae, Bacteria and Eukarya

Front 12

DNA Binding Proteins

Back 12

bind to DNA because of interactions betweeen specific domains of the proteins and specific regions of the DNA molecule

most interact in a sequence specific manner

major groove of DNA is an important site of protein binding

Front 13

Protein-DNA interactions

Back 13

central to the completion and regulation of replication, transcription and translation

Front 14

How are DNA molecules bound to proteins?

Back 14

amino acid side chains of the binding protein associates to the bases and sugar phosphate backbone of the DNA

Front 15

How are DNA binding proteins classified?

Back 15

they are classified by structure or domains

Front 16

Protein domains commonly found in DNA binding proteins

Back 16

1) Zinc Finger

2) Leucine Zipper

3) Helix-turn-helix

Front 17

How do sequence recognition and binding take place in DNA binding proteins?

Back 17

through H-bonds and van der Waals interactions

Front 18

Negative control of transcription

Back 18

Enzymes taht catalyze the synthesis of a specific product are not synthesized if the product is present in sufficent amounts

Front 19

Inducer

Back 19

Substance that initites enzyme induction (ex lactose)

Front 20

Corepressor

Back 20

substance that represses enzyme synthesis (ex arginine)

effectively called effectors

Front 21

Repressor proteins

Back 21

become active after it is bound by the effector

block transcription

Front 22

Operator

Back 22

region of DNA (near the promoter) where the repressor/effector complex binds

single mRNA

Front 23

Operon

Back 23

clutster of genes arranged in a linear, consecutive fashion

when a single regulatory protein controls a single operon

Front 24

Induction

Back 24

involves the binding of an inducer to the repressor

instead of corepressor uses an inducer

Front 25

Positive control of transcription

Back 25

involves a regualtory protein (inducer) that activates the binding of RNA polymerase

example is maltose catabolism in e.coli

Front 26

Activator proteins

Back 26

bind to specific DNA sequences called activator binding sites

activates transcription

bind several hundred bases before promoter

may bend the DNA

Front 27

Regulon

Back 27

when more than one operon is under control of a single regulatory protein

example is maltose catabolism

can be involved with both poistive and negaitve control of transcription

Front 28

Global Control System

Back 28

used by cell to make most efficient use of the available carbon sources

cell always uses glucose first

Front 29

Global Regulatory Systems

Back 29

regulate expression of many unrelated genes siumultaneously

brought about by changes in the environment

Front 30

Catabolite repression

Back 30

ensures that cells always use glucose first

prevents the expression of all other catabolic operons affected by this control mechanism when cells are grown in a medium containing glucose

Front 31

Glucose Effect

Back 31

1) best energy source is chosen

2) cell does not waste energy making enzymes for catabolizing the other sugars

3) if glucose is exhausted, next best sugar taken

Front 32

Stringent Response

Back 32

a global translational control in prokaryotes that represses tRNA and rRNA synthesis during amino acid starvation

Front 33

Alarmones

Back 33

act as the triggers for the stringent response

Front 34

What are the two alarmones?

Back 34

1) guanosine tetraphophate ppGpp

2) Guanosine pentaphosphate (pppGpp)

Front 35

ReIA

Back 35

synthesizes alarmones

monitors ribosome activity

Front 36

How do alarmones inhibit rRNA and tRNA?

Back 36

the interfere with RNA polymerase initions of transcription of genes

Front 37

Gene regulation

Back 37

can be brought about by changing the amount or activity of sigman factors

Front 38

sigma factors

Back 38

recognize different promoter sequences

(ex. e. coli has 7 different sigma factors each recognizing a different promoter)

Front 39

How are sigma factors controlled?

Back 39

1) transcriptional controls (positive or negative)

2) Degradation by proteases (destroys, lowers concentration)

3) Anti-sigma factors (inactive sigma factors)

Front 40

Sigma factors can also be used for these three different circumstances

Back 40

1) Nitrogen assimilation

2) iron transport

3) heat shock

Front 41

Heat Shock Response

Back 41

produces heat shock proteins (sigma 32)

under "normal" conditions sigma 32 is normally degraded very quickly following its synthesis and is more rare in the cell

Front 42

Quorum Sensing

Back 42

sensing mechanism involving signaling molecules that allows cells to survey their environment for cells of their own species

ensures that sufficient cell numbers of a given species are present before eliciting a particular biolgoical response

widespread in gram (-) bacteria

Front 43

Acylated Homoserine Lactone (AHL)

Back 43

bacteria synthesize and secrete this

functions as an inducer that combines with an activator protein and triggers the transcription of specific genes

Front 44

Three examples of Quorum Sensing bacteria

Back 44

1) V. Fischeri (bioluminescent ability)

2) P. Aeruginosa (produce a biofilm that can prevent antibioltic penetration)

3) S. Aureus (produce peptides that damange host cells and disrupt immune system)

Front 45

attenuation

Back 45

mechanism whereby gene expression is controlled after the intiation of RNA synthesis

only seen in prokaryotes

Front 46

Why does attenuation occur?

Back 46

because a portion of the newly formed mRNA folds into a unique stem-loop taht causes cessation of RNA polymerase activity

Front 47

Signal Transduction

Back 47

when a cell receives an external signal through a sensor that then transmits the signal to the regulatory proteins

Front 48

Two components of regulatory systems

Back 48

1) Specific sensor kinase protein

2) Partner response regulator protein

Front 49

Sensor Kinase

Back 49

aka histidine kinases

responsible for self-phosphorylation

receive signal from the environment and phosphorylate one of their specific histdine residues

Front 50

Response regulator

Back 50

DNA binding protein that regulates transcription

phosphoryl group from histine kinase is transferred here