c-di-GMP Flashcards
what is c-di-GMP
a signalling molecule synthesised by DGC proteins with GGDEF and degraded by PDE proteins with either EAL or HD-GYP domains
what is the function of input signalling REC protein domains
they are often associated with GGDEF domains and they are phosphorylated to activate c-di-GMP synthesis
why is c-di-GMP classed as a second messenger
the first messenger is histidine kinase phosphorylating the REC domain
how does c-di-GMP self regulate
it binds to the I site upstream of the catalytic domain which turns off the synthesis of c-di-GMP when levels are too high
why is ancient evolution of the c-di-GMP signalling mechanism implied
there is a similar molecule, c-di-AMP, in archaea
what do c-di-GMP levels indicate in terms of motility
high c-di-GMP levels mean more sessile and low c-di-GMP levels mean more motile
what happens with high c-di-GMP levels in salmonella
cells adhere to each other in biofilms, and curli fimbriae and extracellular polysaccharides are produced
what happens with low c-di-GMP levels in salmonella
altered gene expression results in the expression of flagella
what are the two types of pili and what do they indicate
twitch pili indicate motility and curli pili indicate it’s sessile
what is the trigger enzymes concept
GGDEF/DGC clump together so when one is activated the conformational change activates the rest
how do c-di-GMP and PilZ work together by negative post translational control
they interact with FliM and Mot proteins at the base of the flagella to stop rotation
how do c-di-GMP and PilZ work together by positive transcriptional control
it increases the expression of YcgR and BscA expression which both inhibit motility
what are the roles of c-di-GMP in Caulobacter replication
levels control whether the cell is in stalked or swarmer format, and it controls chromosome replication via CckA kinase/phosphatase
what is the implications of Bdellovibrio having such a large number of PilZ receptors
they are expressed in different places and at different times which reflects their complex life cycle
what DCG proteins are needed in the predatory growth phase of the Bdellovibrio life cycle
DgcA and DgcB to positively regulate prey invasion and motility
what DCG proteins are needed in the axenic growth phase of the Bdellovibrio life cycle
DgcC is required to positively regulate prey-independent growth
what is GVNEF in Bdellovibrio
it is a degenerate GGDEF domain and acts as a receiver domain on receptor protein CgdA
describe the mechanism by which Bdellovibrio contacts prey and initiates invasion
type IV PilA fibres pull the bacteria into contact with the prey cell. at the pole of contact are CdgA and DgcB which synthesises c-di-GMP to initiate predation
how does DgcB self activate
it has a long protein chain which is forced into contact with its fork head FHA domain when in contact with prey. this causes a conformational change and causes activation of the GGDEF domain, also present on the DcgB protein, to stimulate the production of c-di-GMP
in Vibrio cholerae in what ways are motility and virulence affected (2)
at high cell density LuxO cannot repress HapR. this HapR repressed TcpPH which results in the expression of viruence genes. HapR also prevents the expression of DCG proteins, therefore reducing the number of GGDEF domains which would normally promote biofilm formation, thus promoting motility and colonisation
in Pseudomonas aeruginosa describe the process which results in the production of c-di-GMP when present in the lungs
presence on the lung surface is detected by WspA, which transduces this signal to receptor-kinase WspE. this phosphorylates WspR which synthesises c-di-GMp via its GGDEF domain
in Pseudomonas aeruginosa what happens when c-di-GMP binds to PilZ proteins
there is production of cup-protein fimbriae and type III secretion apparatus for lung colonisation and virulence
in Pseudomonas aeruginosa what happens when c-di-GMP binds to non-PilZ protin FleQ
it activates flagellar synthesis. it also represses the pel promoter, inhibiting the synthesis of EPS or biofilm gene expression and therefore promoting motility
where does c-di-GMP bind to FleQ and how is this possible
it binds at the AAA+ATPase walker box motif. this is possible due to the structural similarity of ATPase and c-di-GMP
