The Bacterial Flagellar Hook: Difference between revisions
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The bacterial flagellar hook described in this article is one part of the bacterial flagellum. Please see [[Flagella, bacterial]] | The '''bacterial flagellar hook''' described in this article is one part of the bacterial flagellum. Please see [[Flagella, bacterial]] for an overview of where the hook fits in the flagellum. | ||
==Function== | |||
The flagellar hook is a molecular [http://en.wikipedia.org/wiki/Universal_joint universal joint] that transmits [http://en.wikipedia.org/wiki/Torque torque] from the motor, anchored in the bacterial cell wall, to the [[Flagellar filament of bacteria|flagellar filament]], the relatively rigid helical rod that propels the bacterial cell when rotated. The hook is flexible: it enables the filament to adopt a wide range of angles relative to the motor axis and cell wall, yet continue to be rotated by the motor at all these angles. | The flagellar hook is a molecular [http://en.wikipedia.org/wiki/Universal_joint universal joint] that transmits [http://en.wikipedia.org/wiki/Torque torque] from the motor, anchored in the bacterial cell wall, to the [[Flagellar filament of bacteria|flagellar filament]], the relatively rigid helical rod that propels the bacterial cell when rotated. The hook is flexible: it enables the filament to adopt a wide range of angles relative to the motor axis and cell wall, yet continue to be rotated by the motor at all these angles. | ||
==Structure of the Hook Monomer, FlgE== | ==Structure of the Hook Monomer, FlgE== | ||
The hook filament of ''Salmonella typhimurium'' is composed of about 120 copies of the protein chain FlgE (the product of the [http://ecoliwiki.net/colipedia/index.php/flgE:Quickview gene flgE]), a protein of length 402 amino acids. | |||
===FlgE31 2004=== | |||
<applet load='1wlg' size='350' frame='true' align='right' scene='The_Bacterial_Flagellar_Hook/1wlg_1_mmol/3' caption='Salmonella typhimurium flagellar hook protein FLGE [[1wlg]]'/> | |||
In 2004, Samatey ''et al.'' solved the structure of the mid-portion of the wild-type FlgE of ''Salmonella typhimurium'' by [[X-ray crystallography]] at a [[Resolution|resolution]] of 1.8 Å ([[1wlg]])<ref name="hook1">PMID: 15510139</ref>. The fragment successfully crystallized, designated FlgE31, consisted of amino acids 71-369, of which 71-363 were resolved (72% of the full-length 402-residue protein). Removal of the ends of the full-length chain (domain D0, see below) was required in order to coax the protein to crystallize, instead of forming filaments. | |||
FlgE consists of three domains, D0, D1, and D2. The (<scene name='The_Bacterial_Flagellar_Hook/1wlg_1_mmol/ | FlgE consists of three domains, D0, D1, and D2. The (<scene name='The_Bacterial_Flagellar_Hook/1wlg_1_mmol/3'>initial scene</scene>) at right shows D1 and D2 (D0 having been deleted in order to achieve crystallization, as mentioned above). | ||
{{Template:ColorKey_Amino2CarboxyRainbow}} | {{Template:ColorKey_Amino2CarboxyRainbow}} | ||
Note that D2 consists of a continuous segment of the protein chain, while D1 is made up of discontinuous segments. D0 (not shown, see above) is attached to D1, and D0 forms the inner channel of the hook. D2 forms the outer surface of the hook. | Note that D2 consists of a continuous segment of the protein chain, while D1 is made up of discontinuous segments. D0 (not shown, see above, also discontinuous) is attached to D1, and D0 forms the inner channel of the hook. D2 forms the outer surface of the hook. | ||
<font color="orange"> | |||
[Show evolutionary conservation here after ConSurf server is again available.] | |||
</font> | |||
== Hook Filament Structure == | |||
<table align="right" width="200" ><tr><td rowspan="2"> </td><td>[[Image:Samatey hook copyright nature 2004.gif]]</td></tr><tr><td>Bacterial flagellar hook, rotating simulation, used with permission of [[Fadel A. Samatey Group|Fadel A. Samatey]].</td></tr></table> | |||
In the original monomer structure paper<ref name="hook1" />, the monomer was fitted into an electron density map of about 10 Å resolution, generated by electron cryomicroscopy from hook filaments of ''Salmonella typhimurium'' (see also<ref name="hook2">PMID: 15657146</ref>). Hook filaments are normally curved (at room temperature), but these hook filaments were rendered straight by cold storage, which facilitated image averaging. The D1 and D2 domains of the monomer were independently docked into the map and then ligated. A model of the curved hook filament was generated using symmetry operations that produced the known radius of curvature. This model was then rotated, producing the simulation shown at right. | |||
In 2009, a higher resolution (7.1 Å) electron density map of the straight hook, from cryomicroscopy, was reported by Fujii, Kato and Namba<ref name="hook3">PMID: 19913483</ref>. | |||
{{Clear}} | |||
==Monomer Within the Hook== | |||
<applet size='350' frame='true' align='right' scene='The_Bacterial_Flagellar_Hook/Flagellar_hook_3rings_pdb_gz/3'/> | |||
From the curved model of the hook, here is a short segment just three Flg31 monomers long (<scene name='The_Bacterial_Flagellar_Hook/Flagellar_hook_3rings_pdb_gz/3'>restore initial scene</scene>). Each color represents one of the 11 protofilaments. Since each protofilament is 3 monomers in length, there are 33 monomers in this model. You can see how the Flg31 monomers fit into the hook when <scene name='The_Bacterial_Flagellar_Hook/Flagellar_hook_3rings_pdb_gz/2'>two monomers are highlighted</scene>. | |||
The monomers are slightly larger and more tightly packed than indicated in this model, because this model contains only alpha-carbon atoms. Also the hole in the center of the actual hook filament is much smaller than shown here, because this model lacks the D0 domain that occupies the core of the hook filament. | |||
==Content Attribution== | ==Content Attribution== | ||
The initial content for this article was adapted, with permission, from [http://molvis.sdsc.edu/flagellar_hook/index.htm The Bacterial Flagellar Hook: A Molecular Universal Joint], authored by [[User:Eric Martz]] in 2004-2006 for [[Protein Explorer]]. | The initial content for this article was adapted, with permission, from [http://molvis.sdsc.edu/flagellar_hook/index.htm The Bacterial Flagellar Hook: A Molecular Universal Joint], authored by [[User:Eric Martz]] in 2004-2006 for [[Protein Explorer]]. | ||
==See Also== | |||
* [[Flagella, bacterial]] | |||
* [[User:Fadel A. Samatey/FlgE II/Complete Flagellar Hook Structure|Cryo-EM structure of the complete flagellar hook of ''Campylobacter jejuni'']] (2016) | |||
* [[User:Fadel A. Samatey/FlgE I|X-ray structure of the hook monomers of ''Campylobacter jejuni'' and also of ''Caulobacter cresentus'']] (2016) | |||
* [[Flagellar filament of bacteria]] | |||
* [[Fadel A. Samatey Group]] | |||
==3D structures of flagellar hook protein== | |||
Updated on {{REVISIONDAY2}}-{{MONTHNAME|{{REVISIONMONTH}}}}-{{REVISIONYEAR}} | |||
[[1wlg]] – StFlgE31 – ''Salmonella typhimurium''<br /> | |||
[[2bgy]], [[2bgz]] - StFlgE31 residues 71-363 – Cryo EM<br /> | |||
[[3a69]] - StFlgE31 – Cryo EM<br /> | |||
[[5jxl]] – FlgE – ''Campylobacter jejuni''<br /> | |||
[[5ay6]] – FlgE – ''Caulobacter crescentus''<br /> | |||
==References and Notes== | ==References and Notes== | ||
<references /> | <references /> | ||
[[Category:Topic Page]] | |||