Lecture 17 --Second Messengers Flashcards
intracellular signaling molecules that relay information perceived on the outside of cells to the target molecules inside the cell
secondary messengers
what type of molecules are the known secondary messengers?
multiphosphorylated nucleotides or cyclic nucleotides
which second messenger is involved with stringent response and other nutrient responses
p(pp)Gpp
which secondary messenger is involved in the regulation of metabolic activities and virulence mechanisms (multiple are found in a single bacterium)
cAMP
which secondary messenger is involved in cyst formation, but for the most part has little known about it
cGMP
which secondary messenger is involved in DNA damage-dependent cell cycle control and viability
c-di-AMP
which secondary messenger is involved in the regulation of biofilms as well as virulence and motility
c-di-GMP
are cyclic secondary messengers made up or mainly purines or pyrimidines and which do these include?
mainly purines (adenine and guanine)
what is produced in response to starvation – they show up as “magic spots” in the absence of amino acids, and what is this response known as
alarmones; stringent response
which secondary messengers are associated with the inhibition of rRNA synthesis and upregulation of amino acid biosynthesis during amino acid starvation
ppGpp and pppGpp
why does the stringent response involve a flat period of no growth?
Cells divert resources away from growth and towards the biosynthesis of amino acids
what fold reduction is seen in the rRNA, tRNA, and protein synthesis during stringent response?
10-20 fold reduction
SpoT is found in the stringent response. What is its role with regard to the synthesis of ppGpp
When amino acids are available, the hydrolase domain degrades ppGpp
When there is a lack of amino acids, acyl carrier protein binds to SpoT to activate synthesis of ppGpp
Does amino acid starvation result in charged or uncharged tRNA and how does this affect normal binding
uncharged, instead of binding to A-site of ribosome, acts as a signal for RelA to synthesize ppGpp
Which domain of the RelA/SpoT have catalytic abilities?
The n-terminal (NTD)
Determine strength of synthase activity and hydrolase activity for RelA and SpoT
RelA = strong synthase activity, weak nonfunctional hydrolase activity SpoT = weak synthase activity, strong hydrolase activity
What are the two functions of the CONSERVED TGS and ACT domains in RelA and SpoT
TGS - binds uncharged ACP/determines synthesis/hydrolase activity in SpoT
ACT - interacts with ribosome
What turns off/on RelA and SpoT and how does this change concentrations of ppGpp in the cell
RelA is associated with 1% of ribosomes = base levels of ppGpp always produced
uncharged ACP results in decreased hydrolysis activity, less degraded, more synthesized
what type of second messengers are made up of a single phosphate nucleotide with a cyclic bond arrangement between the sugar and phosphate groups
- are used for hormone and ion channel signaling in eukaryotes
- allosteric effectors of DNA-binding proteins in prokaryotic cells
- have biological significance for a range of protein - ligand interactions
cyclic nucleotides
what two molecules are messengers for glucose catabolism
CRP/CAP and cAMP
- a key secondary messenger that controls catabolite repression
- associated with kinase function in regulation of glycogen, sugar, and lipid metabolism
cAMP (cyclic adenosine monophosphate)
- A CyclicAMP Receptor Protein (CRP) homologue that can control virulence
- reduced in virulence (mutants of adenylate cyclase)
virulence factor regulator
Does CRP expression increase or decrease as pathogen depletes glucose in lungs and forms large biofilm
increase
Serves as a DNA integrity scanning protein to check cell cycle checkpoints and sporulation, controls cell size and envelope stress, widely found in bacteria and a subset of archaea
c-di-AMP
What produces c-di-AMP and what degrades it
diadenylate cyclase (DAC); phosphodiesterase
What is DarR a receptor protein for?
c-di-AMP
Why was it so difficult to discover c-di-AMP
It is essential, disA, dacA, and dacB mutants do not work –> shows required for normal cellular growth
which secondary messenger acts as an effector of the cellulose synthase enzyme
c-di-GMP
