The Stringent Response

Question 1

The Stringent Response

Answer 1

Bacterial stress response to nutritional starvation e.g. amino acid, carbon and phosphate

Question 2

NDK

Answer 2

nucleoside diphospate kinase GDP -> GTP

Question 3

SPOT*

Answer 3

Bifunctional (p)ppGpp synthase/hydrolase SpoT regulatory enzyme

Mn2+ cofactor

Question 4

(p)ppGpp

Answer 4

ppGpp binds to alpha subunits in ribosomes and changes specificity to certain promoters

ppGppp is a signal molecule that destabilises promoters and inhibits transcription initiation w Dksa

Question 5

RelA

Answer 5

ppGpp synthase
found in every 1 out of 200 ribosomes
activated by uncharged tRNA in ribosome A site

Question 6

Relaxed mutants

Answer 6

mutant RelA/Spot genes + don’t show stringent response when starved of nutrients

Question 7

How is ppGppp formed

Answer 7

RelA and SpoT pathways

Question 8

RelA pathway

Answer 8

uncharged tRNA in A site of ribsome stalls protein synthesis
RelA triggered via conformation change into open form and can cause ppGppp synthesis

Question 9

SpoT pathway

Answer 9

Synthetase ppGppp from GTP

Question 10

Magic Spot 1

Answer 10

ppGpp

Question 11

Magic Spot 2

Answer 11

ppGppp

Question 12

Acyl Carrier Protein

Answer 12

Cofactor of both fatty acid and polyketide biosynthesis machinery.

Interacts w SpoT to shift between synthase and hydrolase

Question 13

RSH

Answer 13

RelA/SpoT Homologue (RSH) protein family

Question 14

rplL gene

Answer 14

encodes ribosomal protein L12

Question 15

rplA gene

Answer 15

encodes ribosomal protein L1

Question 16

evidence for translational autorepression

Answer 16

even when chromosome copies are increased, gene product numbers remain the same

Question 17

rrn operon

Answer 17

Ribosomal RNA operon
UP|P|16S|tRNA|23S|5S|tRNA

Question 18

H-NS

Answer 18

Histone like nucleoid restructuring protein
Binds to rrn promoter and polymerises around it
Inhibits RNAP binding to promoter
Binds 2 distant regions of DNA together

Question 19

UP element

Answer 19

UP elements interact directly with the C-terminal domain of the α subunit of RNAP (αCTD) in holoenzymes containing σ70 or alternative σ factors
Increase affinity of RNAP to promoter
AT rich regions upstream of promoters

Question 20

FIS

Answer 20

Factor for inversion stimulation
Transcriptional activation of rRNA and tRNA operons
Binds to promoter near UP elements
Formation of transcription factories

Question 21

rrn promoter

Answer 21

strong/tight RNAP binding
consensus sequence
forms short lived open complexes (held open by ATP/GTP)

Question 22

Dksa

Answer 22

DNAK suppressor protein
Global transcriptional regulator
Works in conjunction with ppGpp
RNAP binding factor - causes formation of ppGpp binding site on RNAP secondary channel