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From Proteopedia
Contents |
CheA-CheY Interactions in a Two-Component Signal Transduction System
Introduction to Chemotaxis
- Chemotaxis is the coordinated movement by a cell in response to certain chemicals in the environment, such as attractants and repellants.
- Escherichia coli coordinate flagellar movements in response to a gradient of nutrients, or attractants. The transmembrane receptor senses chemicals. The two-component system transduces the signal. The outcome is a change in flagellar motion.
- E. coli have peritrichous flagella, meaning they are all over the cell exterior.
- Flagellar motion is the alternation between running and tumbling. Running is described as moving in a straight line, generally towards a higher concentration of attractants. This is accomplished by bundling the flagella. Tumbling is described as a change in direction, generally towards lower concentrations of attractants. This is accomplished via dissociation of the flagella.
- Bundling and dissociation are accomplished by rotation of the flagellar motor. Counterclockwise rotation of the flagella motor results in running. This is the default state of the motor. Clockwise rotation of the flagellar motor results in tumbling and requires a signaling pathway. This signaling is done via a two-component system consisting of a histidine kinase and a response regulator.
Chemotaxis Components
VIDEO OF PLAYERS
- Histidine kinase (HK) = CheA, found as a dimer
- P1 = phosphotransfer (His48)
- P2 = CheY binding
- P3 = dimerization
- P4 = ATP kinase
- P5 = CheW site
- Response regulator (RR) = CheY
- Asp57 = phosphate accepting site
- Roles of CheB, CheR and CheZ
Phosphotransfer Events
VIDEOS OF PHOSPHORYLATION EVENTS
- Autophosphorylation of CheA at His48
- Phosphotransfer of labile phosphate to CheY at Asp57
- Diffusion of CheY away from CheA and towards FliM at flagellar motor
- Increase in attractant (serine) concentration
- Serine binds to receptor and blocks auto-phosphorylation of CheA
- CheY does not receive phosphate
- Motor resets and results in counterclockwise rotation and running motion
Learning Objectives
- How do you get specific interactions between CheA and CheY?
- What is the role of P1 in the interaction?
- What is the role of P2 in the interaction?
- How do you position His48 and Asp57 to allow phosphotransfer?
Specificity of CheA-CheY Interactions
TUTORIAL/VIDEO
Roles of CheA Domains
Role of P1 in CheA-CheY Interactions
TUTORIAL/VIDEO
- Low affinity binding
- CheA-P1 has low affinity for CheY
- Phe8 and Glu15 play role in correct orientation of components for phosphotransfer. Mutations result in significant decreases in phosphotransfer rate.
- Essential to orientation
Role of P2 in CheA-CheY Interactions
TUTORIAL/VIDEO
- High affinity binding
- CheA-P2 has high affinity for CheY. Phe214 on CheA serves as anchor site. Mutations of Phe214 result in four-fold (?) decrease in binding affinity.
- Essential to docking
Orientation Requirements of His48 and Asp57 for Phosphotransfer
TUTORIAL/VIDEO
CheY-FliM Interactions and Conformational Change
IMAGES/TUTORIAL/VIDEO
