AMC (Inhibition of) cell wall synthesis and division in e coli

cell cycle of e coli (5)

cell division/birth, elongation, z ring formation, divisome assembly, constriction

what does elongation require

longitudinal peptidoglycan synthesis

what determines shape of e coli

peptidoglycan layer

what does insertion of a building unit for e coli membrane

PBPs

what does penicillin affect

inhibits transpeptidation

way to grow more soil bacteria (maybe capable of producing abx)

iChip - small seperate chambers (wells) filled w/ soil suspension, try to have 1 soil bacterium per well, seal w/ semi-permeable membrane - solutes can pass but not bacteria or compounds (eg abx) that are produced, grow in soil

advantages of iChip

culture “uncultivatable” soil bacteria in soil, then can test extracts for antimicrobial activity, purify and characterize active compound, identify target, identify producing bacterium - eg teixobactin

2 modes of peptidoglycan (PG) synthesis

elongation or length growth - by random insertion of PG units in the cylindrical wall
cell division - complete new synthesis of the cell poles

what is the next stage

FtsZ polymerizes into ring at midcell

FtsZ descr

essential protein in bacteria and archaea that drives cell division by forming a ring-shaped structure at the middle of the cell; structural tubulin homologue - essential, conserved and abundant

how does FtsZ work

binds to membrane via ZapA (promotes bundling) and FtsA (ATPase, actin homologue), polymerizes to form a contractile ring, recruits late divisome proteins

GTPase and FtsZ

GTP couples FtsZ monomers head to tail - hydrolysis curves and destabilizes interaction, very dynamic, half life or ring only 10s, diameter decreases in this process

is FtsZ a good antimicrobial target?

Yes: essential for survival, conserved in several bacterial genera, catalytic activity/binding of ligands, developing resistance by mutagenesis of target should not be easy, structure known
No: should not have close human homologue to avoid toxicity, accessible to drugs (subcellular location of target is important), not abundant (lower [] of drugs will be sufficient)

what else is recruited to the divisome

so so much, im not gonna put it soz (eg ZipA - stabilizes Z ring)

what is important in the divisome

FtsQ - hub for interactions in divisome, regulatory role in septal PG synthesis

is FtsQ a good target?

yes: target essential for survival, conserved in several bacterial genera, should not have a close human homologue to avoid toxicity, developing resistance by mutagenesis of target should not be easy, accessible to drugs (subcellular location of target is important), not abundant (lower [] of drugs will be sufficient), structure known
maybe: catalytic activity/binding of ligands

next steps w/ FtsQ

map interactions FtsQ - biochemical and structural analysis
screening - in siluco design/chemical synthesis of abx that inhibit critical interactions of FtsQ

structure of FtsQ-B

structure validated by structure guided mutants, structure based design of small molecule inhibitors of FtsQ-FtsB interaction, design of peptidomimetics that block FtsQ-FtsB interaction

covalent inhibitory peptidomimetics

less initial affinity required, allows more extensive modification/truncations, lower [] required, efficient competition w/ FtsBL dimer for FtsQ binding