osmolarity Flashcards
where does autophosphorylation occur
in the catalytic domain of the dimerised sensor kinase. it is then moved to the histidine kinase domain
does the catalytic domain give the Pi to the histidine kinase domain of the same monomer
sometimes- this is called cis. if it gives it the the other monomer of the dimer it is trans
when do response regulators dimerase
only after the response regulators have been phosphorylated can they be dimerised to bind to both DNA promoters and RNAP
how is phosphotransfer more easily seen
using BeF3 instead of PO4- it mimics its function but is more visible
what is the fingerprint
amino acids surrounding H and D of SK and RR respectively which interact with each other to bring the two components together
what is second site suppression
mutations in the fingerprint can stop the two components being brought together and prevent transcription. if the bacteria are left to reproduce and mutate they can compensate for the mutations and restore transcriptional function
what is pathway insulation
a two- component regulator existed but id replicated. one of the copies retained function whilst the other evolved. eventually they became insulated from each other with two distinct functions
what is osmolarity
a measure of the levels of dissolved substances in a solution
how does EnvZ- OmpR respond to osmolarity
it regulated the expression of two outer- membrane poring OmpC and OmpF
how do OmpR-P levels reflect osmolarity
when osmolarity is low there is little OmpR-P, when osmolarity is high there is more
how are ompF and ompC different
ompF had a diameter of 1.16nm, ompC has one of 1.08nm
which porins are expressed at high osmolarity
this is usually in the gut. ompC is expressed to maximise food intake. ompF is not expressed to prevent intake of bile salts which would damage the bacteria
which porins are expressed at low osmolarity
this is usually in open water. ompF is expressed to maximise food intake. ompC is not expressed as it would be wasteful to express it as well as ompF
how is water intake involved
in low osmolarity water briefly enters and the cell swells. in high osmolarity water briefly exits, ions enter and the cell shrinks. these changes cause the bacteria to respond to the osmolarity changes quickly to prevent damage
what does OmpR-P bind at high osmolarity
in binds to low affinity boxes- the C box in ompC activated transcription, and the C/Fe/Fd boxes in ompF which causes the promoter to loop (with the help of IHF) and inhibits transcription
what does OmpR-P bind at low osmolarity
high affinity boxes- FabC box in ompF which activated transcription. it cannot bind to any regions in the ompC promoter so there is no transcription
which amino acids are involved in bonding of the RNAP and the regulator domain
V264, D280 and Q283 in the alpha C terminal of the RNAP interact with P179, S181 and R182 in the regulator domain. there is evidence of second site suppression here
what else does OmpR-P regulate the expression of
it regulates the expression of omrA and B which prevent the translation of ompT mRNA
what is the role of OmpR-P in disease
it is essential is infections of the urinary tract- without in the mutants couldn’t respond to changes in osmolarity in the urine
how does EnvZ change
the histidine kinase domain changes in response to osmolarity- the loop is longer in low osmolarity and shorter in high osmolarity
what is the role of procaine
it is an external factor which can alter EnvZ by artificially changing the shape of the sensor
