11730557
Description
Flashcards by Candice Young, updated more than 1 year ago
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Created by Candice Young
over 6 years ago
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| Question | Answer |
| cytoskeletal proteins | needed to create distinct bacterial shapes and are sometimes required for viability!! ANALOGS TO US: Actin = MreB Tubulin = FtsZ Intermediate filaments = CreS (crescentin) |
| MreB | polymerizes (using ATP) into filaments like actin; structure closely resembles actin deplete MreB: PG synthesis continues, but is not correctly regulated --> cell wall loses shape, cell lyses located along all of cell throughout growth and division |
| Effect of MreB/C on PBPs | PBPs become mislocalized if MreB or C depleted/when MreB filaments depolymerized |
| MreBCD | form complex (PG "factories) that positions and regulates PG machinery along lateral cell walls --> includes transglycosylases, trans-peptidases (PBP2, RodA), enzymes that make PG monomers (MraY, MurG) without MreBCD: PBP2 mislocalized --> lateral cell walls not made normally --> cells become swollen and lyse |
| How does MreB mobilize around the cell? | Driven by the synthesis of PG: MreB associates with the PBP complex via lipid-linked PG precursors (products of MurG and MraY) Without precursors: MreB disassembles, no movement cause by PG synthesis |
| Crescentin (CreS) | responsible for the curved shape of Caulobacter/etc; similar to intermediate filaments |
| What does curvature mean for the cell? | Curved cells have an advantage in surface attachment under flow cytometry conditions --> better access to nutrients |
| How does curvature help with surface attachment? | curved cells attach to surfaces w/ polar stalk & holdfast at tip --> during growth, pili built at pole opposite the stalk --> new pili stick to surface --> at division the new daughter cell is already attached curved cells have the advantage because new pili points down (unlike for straight)! |
| What proteins act at the division site to form a new septa? | WT FtsZ: forms ring at site of cell division between the two replicated chromosomes |
| FtsZ | helps with cell division and septa formation tubulin homolog; filaments of this form a Z ring that constricts to drive cell devision assembly site for the divisome |
| divisome | large protein complex that spans IM + synthesizes septal cell wall! subunits are essential for viability; studied using ts mutations or depletion -FtsA & ZipA: tether FtsZ to the membrane -FtsW: PBP3 --> septum; transglycosylase -FtsK: chromosome segregation -FtsQLB: triggers Z-ring & cell constriction |
| What drives the motion of PBPs at the septum? | FtsZ treadmilling (building concentric rings moving inward over time) FtsZ GTPase activity blocked --> PBPs stop moving around circumference |
| How does FtsZ cause circular constriction at division site? | 1) FtsZ GTPase activity: FtsZ-GDP filaments are bent from original FtsZ-GTP 2) FtsZ-GDP anchored to the cytoplasmic membrane --> PBPs build PG along a bent/curved path 3) FtsZ treadmills in curved paths at division site --> drives the motion of PBPs! |
| minCDE mutant | normal cells, long rods, and minicells central AND polar division sites used |
| minE mutant | long filaments minCD blocks division everywhere |
| MinC and MinD | Rapid pole-to-pole oscillation MinC and MinD form “tube” on cytoplasmic membrane at one end of the cell --> every 20s, migrate to the opposite pole |
| Min E | MinE forms ring at edge of MinCD zone. E ring moves toward pole containing MinCD --> MinC and MinD are released --> set up a new polar zone at the other end, away from MinE |
| mechanism for Min Oscillation | 1) MinC bound to MinD --> MinC shortens + inhibits FtsZ filaments bundling 2) MinD-ATP binds IM, carries MinC with it --> hydrolyzes ATP --> released from IM 3) MinE binds to MinD and IM --> MinE stimulates ATPase activity of MinD --> releases MinCDE from membrane. 5) MinE rapidly rebinds to the membrane (and itself), near where it just fell off. 6) In cytoplasm, MinD exchanges ADP for ATP --> rebinds to the membrane (if near MinE: expelled from the membrane; if far from MinE set up a new zone of MinCD 7) Net result: is that MinC, the FtsZ inhibitor, spends most time at cell poles and very little time at the midcell!! |
| nucleoid occlusion | nucleoid gives off a signal preventing FtsZ ring formation nearby EX: SlmA binds to SBS in E. coli genome; SBS NOT present near terminus (located in center of cell near division plane); SlmA + SBS inhibits FtsZ polymerization, but SlmA alone does not |
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