User:Elizabeth R. Haglin/Sandbox 1: Difference between revisions

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[[Image:Chemotaxis.png|300px|right|thumb|Chemotaxis overview <ref>PMID:15573139</ref>]]

__TOC__

The '''Histidine Kinase (HK) CheA''' relays signals from the transmembrane chemoreceptors (methyl-accepting chemotaxis proteins/MCPs) to regulate bacterial chemotaxis. The functional form of CheA exists as a dimer and is associated to the receptors through a coupling protein CheW. Kinase activity of CheA depends on signals received from the receptor via an ATP-dependent phosphoryl transfer the trans monomer of dimeric CheA. The phosphoryl group is subsequently transferred to the response regulator (RR) CheY and carried throughout the cell to interact with the flagellar motor and control cellular mobility and directionality.

== Biological context ==

~~[[Image:Chemotaxis~~.~~png|250px|left|thumb|Chemotaxis overview <ref>PMID:15573139</ref>]]~~

'''Histidine Kinase (HK) CheA''' relays signals from the transmembrane chemoreceptors (methyl-accepting chemotaxis proteins/MCPs) to regulate bacterial chemotaxis. The functional form of CheA exists as a dimer and is associated to the receptors through a coupling protein CheW. Kinase activity of CheA depends on signals received from the receptor via an ATP-dependent phosphoryl transfer the trans monomer of dimeric CheA. The phosphoryl group is subsequently transferred to the response regulator (RR) CheY and carried throughout the cell to interact with the flagellar motor and control cellular mobility and directionality.

Chemotaxis is a behavior used by most motile flagellated bacteria, like E. coli and T. maritima, to modify their swimming pattern in response to environmental stimuli. Directionality is controlled by the counter-clockwise (CCW) running or clockwise (CW) tumbling motion of the flagellar motor, which in turn is regulated by large arrays of a two-component signal transduction complex responsible for sensing extracellular chemical concentration gradients. Upon binding of a chemical ligand, the MCPs regulate ATP-dependent trans-autophosphorylation activity of the histidine kinase CheA. A repellent binding event leads to increases in phosphorylated CheA (CheA-P) and a subsequent increase in phosphorylation of CheA’s binding partner and CheY. Phosphorylated CheY (CheY-P) has a high affinity for the flagellar motor switch protein FliM and at increased concentrations will change the motor rotation from CCW to CW, leading to tumbling. Likewise, attractant binding inhibits CheA phosphorylation so unphosphorylated CheY dominates, the motor switch CCW motion is unaffected, and the cell maintains smooth swimming. The CheY-P signal is additionally regulated by the phosphatase CheZ. Ultimately, the flux of phosphoryl groups governs the mobility response to external stimuli.

Chemotaxis is a behavior used by most motile flagellated bacteria,like ''E. coli'' and ''T. maritima'', to modify their swimming pattern in response to environmental stimuli. Directionality is controlled by the counter-clockwise (CCW) running or clockwise (CW) tumbling motion of the flagellar motor, which in turn is regulated by large arrays of a two-component signal transduction complex responsible for sensing extracellular chemical concentration gradients. Upon binding of a chemical ligand, the MCPs regulate ATP-dependent trans-autophosphorylation activity of the histidine kinase CheA. A repellent binding event leads to increases in phosphorylated CheA (CheA-P) and a subsequent increase in phosphorylation of CheA’s binding partner and CheY. Phosphorylated CheY (CheY-P) has a high affinity for the flagellar motor switch protein FliM and at increased concentrations will change the motor rotation from CCW to CW, leading to tumbling. Likewise, attractant binding inhibits CheA phosphorylation so unphosphorylated CheY dominates, the motor switch CCW motion is unaffected, and the cell maintains smooth swimming. The CheY-P signal is additionally regulated by the phosphatase CheZ. Ultimately, the flux of phosphoryl groups governs the mobility response to external stimuli.

== Structure ==

[[Image:CheA_domains.png|410px|left|thumb|CheA Domains <ref>PMID: 22494339</ref>]]

'''CheA''' exists as a homodimer of 71-kDa subunits. Each monomer catalyzes an ATP-dependent ''trans''-phosphorylation of a histidine. A monomer contains five domains (P1-P5 from N- to C-terminus) connected by highly dynamic linkers of various lengths. Each domain has a distinct function.Due to the size of CheA, the solved structures available to date do not have all five domains. The PDB files included in this proteopedia page are <scene name='User:Elizabeth_R._Haglin/Sandbox_1/P3p4p5/3'>1B3Q</scene> with a dimer of P3P4P5 and <scene name='User:Elizabeth_R._Haglin/Sandbox_1/P1_p2_chey/2'>2LP4</scene> which contains a P1P2-CheY complex.

*P1: histidine phosphotransfer domain (HPt) mediates phosphate transfer from ATP to CheY

*P2: CheY binding domain releases CheY-P upon small conformational changes

*P3: dimerization domain

*P4: ATP-binding catalytic domain

*P5: autophosphorylation regulatory domain relays signal input to P4 from the chemoreceptor and CheW

=== P1P2: Histidine phosphotransfer domains ===

<scene name='User:Elizabeth_R._Haglin/Sandbox_1/P1p2_active_site/1'>Active site</scene>

=== P3P4P5: Kinase core domains ===

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== Additional 3D structures of CheA ==

</StructureSection>

== References ==

</~~StructureSection~~>

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-<Structure load='1b3q' size='500' frame='true' align='right' caption='Structure of CheA  (PDB entry [[1b3q]]) scene='User:Elizabeth_R._Haglin/Sandbox_1/P3p4p5/1'>
+<Structure load='1b3q' size='500' frame='true' align='right' caption='Structure of histidine kinase CheA' scene='User:Elizabeth_R._Haglin/Sandbox_1/P3p4p5/3'>
+[[Image:Chemotaxis.png|300px|right|thumb|Chemotaxis overview <ref>PMID:15573139</ref>]]
 __TOC__
-The '''Histidine Kinase (HK) CheA''' relays signals from the transmembrane chemoreceptors (methyl-accepting chemotaxis proteins/MCPs) to regulate bacterial chemotaxis. The functional form of CheA exists as a dimer and is associated to the receptors through a coupling protein CheW. Kinase activity of CheA depends on signals received from the receptor via an ATP-dependent phosphoryl transfer the trans monomer of dimeric CheA.  The phosphoryl group is subsequently transferred to the response regulator (RR) CheY and carried throughout the cell to interact with the flagellar motor and control cellular mobility and directionality.
 == Biological context ==
-[[Image:Chemotaxis.png|250px|left|thumb|Chemotaxis overview <ref>PMID:15573139</ref>]]
+'''Histidine Kinase (HK) CheA''' relays signals from the transmembrane chemoreceptors (methyl-accepting chemotaxis proteins/MCPs) to regulate bacterial chemotaxis. The functional form of CheA exists as a dimer and is associated to the receptors through a coupling protein CheW. Kinase activity of CheA depends on signals received from the receptor via an ATP-dependent phosphoryl transfer the trans monomer of dimeric CheA.  The phosphoryl group is subsequently transferred to the response regulator (RR) CheY and carried throughout the cell to interact with the flagellar motor and control cellular mobility and directionality.
-Chemotaxis is a behavior used by most motile flagellated bacteria, like E. coli and T. maritima, to modify their swimming pattern in response to environmental stimuli. Directionality is controlled by the counter-clockwise (CCW) running or clockwise (CW) tumbling motion of the flagellar motor, which in turn is regulated by large arrays of a two-component signal transduction complex responsible for sensing extracellular chemical concentration gradients.  Upon binding of a chemical ligand, the MCPs regulate ATP-dependent trans-autophosphorylation activity of the histidine kinase CheA. A repellent binding event leads to increases in phosphorylated CheA (CheA-P) and a subsequent increase in phosphorylation of CheA’s binding partner and CheY. Phosphorylated CheY (CheY-P) has a high affinity for the flagellar motor switch protein FliM and at increased concentrations will change the motor rotation from CCW to CW, leading to tumbling. Likewise, attractant binding inhibits CheA phosphorylation so unphosphorylated CheY dominates, the motor switch CCW motion is unaffected, and the cell maintains smooth swimming.  The CheY-P signal is additionally regulated by the phosphatase CheZ. Ultimately, the flux of phosphoryl groups governs the mobility response to external stimuli.
+Chemotaxis is a behavior used by most motile flagellated bacteria,like ''E. coli'' and ''T. maritima'', to modify their swimming pattern in response to environmental stimuli. Directionality is controlled by the counter-clockwise (CCW) running or clockwise (CW) tumbling motion of the flagellar motor, which in turn is regulated by large arrays of a two-component signal transduction complex responsible for sensing extracellular chemical concentration gradients.  Upon binding of a chemical ligand, the MCPs regulate ATP-dependent trans-autophosphorylation activity of the histidine kinase CheA. A repellent binding event leads to increases in phosphorylated CheA (CheA-P) and a subsequent increase in phosphorylation of CheA’s binding partner and CheY. Phosphorylated CheY (CheY-P) has a high affinity for the flagellar motor switch protein FliM and at increased concentrations will change the motor rotation from CCW to CW, leading to tumbling. Likewise, attractant binding inhibits CheA phosphorylation so unphosphorylated CheY dominates, the motor switch CCW motion is unaffected, and the cell maintains smooth swimming.  The CheY-P signal is additionally regulated by the phosphatase CheZ. Ultimately, the flux of phosphoryl groups governs the mobility response to external stimuli.
 == Structure ==
+[[Image:CheA_domains.png|410px|left|thumb|CheA Domains <ref>PMID: 22494339</ref>]]
+'''CheA''' exists as a homodimer of 71-kDa subunits. Each monomer catalyzes an ATP-dependent ''trans''-phosphorylation of a histidine.  A monomer contains five domains (P1-P5 from N- to C-terminus) connected by highly dynamic linkers of various lengths.  Each domain has a distinct function.Due to the size of CheA, the solved structures available to date do not have all five domains.  The PDB files included in this proteopedia page are <u><scene name='User:Elizabeth_R._Haglin/Sandbox_1/P3p4p5/3'>1B3Q</scene></u> with a dimer of <b><font color='deepskyblue'>P3</font><font color='limegreen'>P4</font><font color='mediumorchid'>P5</font></b> and <u><scene name='User:Elizabeth_R._Haglin/Sandbox_1/P1_p2_chey/2'>2LP4</scene></u> which contains a <b><font color='gold'>P1</font><font color='hotpink'>P2</font>-<font color='red'>CheY</font></b> complex.
+*<b><font color='gold'>P1</font></b>: histidine phosphotransfer domain (HPt) mediates phosphate transfer from ATP to CheY
+*<b><font color='hotpink'>P2</font></b>: CheY binding domain releases CheY-P upon small conformational changes
+*<b><font color='deepskyblue'>P3</font></b>: dimerization domain
+*<b><font color='limegreen'>P4</font></b>: ATP-binding catalytic domain
+*<b><font color='mediumorchid'>P5</font></b>: autophosphorylation regulatory domain relays signal input to P4 from the chemoreceptor and CheW
 === P1P2: Histidine phosphotransfer domains ===
+<scene name='User:Elizabeth_R._Haglin/Sandbox_1/P1p2_active_site/1'>Active site</scene>
 === P3P4P5: Kinase core domains ===
@@ Line 18: / Line 25: @@
 == Additional 3D structures of CheA ==
+</StructureSection>
 == References ==
+<references/>
-</StructureSection>