Environmental Sensing Flashcards
What are the components of two-component regulatory systems?
-Component 1: The sensor Histidine Protein Kinase (transmembrane proteins)
-Component 2: The response Regulator
What does histidine protein kinases do?
-has sensors that consist of two domains: 1) a variable response to the domain (variable to tell you they are actively evolving) and 2) a Conserved transmitter domain
-Sensors usually form dimers and exhibit autokinase activity. ATP binds to one subunit and phosphorylates the other in a process known as transphosphorylation
-Sensor transmits the phospho-group from its histidine residue to an aspartate residue on the response regulator
What do CheY and CheB do
-Consist of two domains: 1) conserved receiver domain containing the aspartate residue 2) variable regulator
-Two response regulators involved in chemotaxis, don’t bind DNA at all but instead modulate the activity of other proteins
Describe the EnvZ/OmpR system of E. coli
1) signal binding causes activation of the autokinase resulting in ATP hydrolysis and phosphorylation (p) of a histidine (H) on the phosphotransferase sub-domain
-The phosphoryl group is transferred to the aspartyl group (D) on the response regulator
Describe chemotaxis
-chemical stimuli
-gradient sensing mechanism allows prokaryotes to compare concentrations of a chemical over a short time interval
Describe Phototaxis
-light stimuli
Describe scotophobotaxis
darkness stimuli
How do flagella impact taxis
Are flagella conserved or variable between bacterial species?
Between bacteria, flagella are structurally very similar although they come in different configurations
draw different configurations of bacterial flagellar arrangements
What are random walks?
-bacteria will move randomly due to the absence of a chemical gradient
-includes running and tumbing
What is a biased random walk and how is it different from a random walk
-In the presence of a gradient of attractant or repellant, bacteria bias their random walk to include longer runs and fewer tumbles up the concentration gradient of an attractant or down the concentration gradient of a repellant
How is tumbling different from walking
Tumbling means the flagellum is in a clockwise rotation and will change direct of the bacteria while walking means the flagellum is in a counterclockwise rotation
What do sensory proteins do regarding flagella
-The binding sites in the MCP domains are different for attractants and repellants
-binding of an attractant to the MCP stimulates a signal transduction cascade that eventually affects the direction of flagellar motion
Describe the purpose of CheA, CheY, CheZ, FliM. Describe the pathway, what phosphorylates or de-phosphorylates what, and what occurs in mutants that are missing CheZ and CheY
-Phosphorylated CheA transfers its phosphate to the aspartate residue on the response regulator CheY
-Phosphorylated CheY interacts with FliM, a component of the flagellar moto, to change the direction of rotation from counterclockwise to clockwise resulting in tumbling
1)In response to the attractant binding the MCPs, CheA decreases its rate of autophosphorylation (b/c you want to continue to swim toward the attractant)
2) In the absence of CheA-P, CheY remains unphosphorylated and cannot interact with FliM. CheZ helps keep CheY phosphorylated in the presence of low levels of CheA-P
3) Disruption of the CheY-FilM interaction switches the flagellar to counterclockwise rotation and smooth swimming
Describe the role of cell-cell signaling in B. subtilis
Describe the role of transcriptional regulation in B. subtilis
Describe the role of cell type-specific proteolysis in B. subtilis
What is an endospore? What elements can it survive in?
-Spores that lie dormant for hundreds, thousands, perhaps even millions of years and then, at the mere whiff of amino acids, germinate to form viable organisms
-Cann survive harsh environmental conditions such as high temperatures, UV light, and organic solvents
Describe the sporulation cascade step by step. Draw out each step including Sigma F, Sigma E, Sigma G, Sigma K, Sigma H, Spo0A
How does the EnvZ/OmpR system of E. coli react to changes in osmolarity?
-high osmolarity results in the phosphorylation of OmpR
-OmpC expression increases as OmpR-P concentration in the cytoplasm increases
-OmpF expression increases as OmpR concentration in the cytoplasm increases
-There is a reciprocal relationship between OmpC and OmpF expression
Describe the role of Quorum sensings in B. subtilis
