Sandbox Reserved 473: Difference between revisions

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Molecular motors convert chemical energy to mechanical energy by causing reactions that power directed conformational changes, resulting in motion.

In solution or in a free state, kinesin has ADP bound to each head or motor domain. Once kinesin attaches to a microtubule and changes its conformation slightly, ADP can be exchanged for high-energy ATP. This action causes the <scene name='Sandbox_Reserved_473/Neck/1'>neck linker</scene> to “zipper” into a binding pocket in the motor domain (near a structure called the <scene name='Sandbox_Reserved_473/Relay_helix/1'>relay helix</scene>). The zippering causes the second head of the kinesin to swing around and land on the microtubule ahead of the first head <ref name = "movie">Milligan, R. (2000.) An animated model for processive motility by conventional kinesin (movie). Retrieved from http://www.scripps.edu/milligan/research/movies/kinesin_text.html</ref>. The second head may reach the microtubule either by active movement, by simple diffusion, or by a combination of the two <ref name = "woehlke"/>. While the second head binds the microtubule, ATP hydrolysis occurs at the first head, releasing it from the microtubule. ATP hydrolysis also “unzippers” the neck linker from the relay helix, resetting the conformation for another reaction. It is remarkable that ATP binding and hydrolysis create tiny conformational changes in the active site (on the order of angstroms) that can lead to large overall conformational changes in the entire protein (on the order of nanometers). This phenomenon is known as mechanical amplification <ref>Vale, R.D. and Milligan, R.A. (2000.) The way things move: looking under the hood of molecular motor proteins. Science 288(5463): 88-95.</ref>.

In solution or in a free state, kinesin has <scene name='Sandbox_Reserved_473/Atp_binding_site/3'>ADP</scene> bound to each head or motor domain. Once kinesin attaches to a microtubule and changes its conformation slightly, ADP can be exchanged for high-energy ATP. This action causes the <scene name='Sandbox_Reserved_473/Neck/1'>neck linker</scene> to “zipper” into a binding pocket in the motor domain (near a structure called the <scene name='Sandbox_Reserved_473/Relay_helix/1'>relay helix</scene>). The zippering causes the second head of the kinesin to swing around and land on the microtubule ahead of the first head <ref name = "movie">Milligan, R. (2000.) An animated model for processive motility by conventional kinesin (movie). Retrieved from http://www.scripps.edu/milligan/research/movies/kinesin_text.html</ref>. The second head may reach the microtubule either by active movement, by simple diffusion, or by a combination of the two <ref name = "woehlke"/>. While the second head binds the microtubule, ATP hydrolysis occurs at the first head, releasing it from the microtubule. ATP hydrolysis also “unzippers” the neck linker from the relay helix, resetting the conformation for another reaction. It is remarkable that ATP binding and hydrolysis create tiny conformational changes in the active site (on the order of angstroms) that can lead to large overall conformational changes in the entire protein (on the order of nanometers). This phenomenon is known as mechanical amplification <ref>Vale, R.D. and Milligan, R.A. (2000.) The way things move: looking under the hood of molecular motor proteins. Science 288(5463): 88-95.</ref>.

The reaction repeats over and over again as the kinesin binds and hydrolyzes one ATP for each 8-nanometer step it takes <ref name = "pdb">Goodsell, D. (2005.) Kinesin. RCSB Protein Data Bank. Retrieved from http://www.rcsb.org/pdb/101/motm.do?momID=64</ref>. Once bound to the microtubule, kinesin can take several steps without falling off, an ability known as processivity.

Sandbox Reserved 473: Difference between revisions

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 Molecular motors convert chemical energy to mechanical energy by causing reactions that power directed conformational changes, resulting in motion.
-In solution or in a free state, kinesin has ADP bound to each head or motor domain. Once kinesin attaches to a microtubule and changes its conformation slightly, ADP can be exchanged for high-energy ATP. This action causes the <scene name='Sandbox_Reserved_473/Neck/1'>neck linker</scene> to “zipper” into a binding pocket in the motor domain (near a structure called the <scene name='Sandbox_Reserved_473/Relay_helix/1'>relay helix</scene>). The zippering causes the second head of the kinesin to swing around and land on the microtubule ahead of the first head <ref name = "movie">Milligan, R. (2000.) An animated model for processive motility by conventional kinesin (movie). Retrieved from http://www.scripps.edu/milligan/research/movies/kinesin_text.html</ref>. The second head may reach the microtubule either by active movement, by simple diffusion, or by a combination of the two <ref name = "woehlke"/>. While the second head binds the microtubule, ATP hydrolysis occurs at the first head, releasing it from the microtubule. ATP hydrolysis also “unzippers” the neck linker from the relay helix, resetting the conformation for another reaction. It is remarkable that ATP binding and hydrolysis create tiny conformational changes in the active site (on the order of angstroms) that can lead to large overall conformational changes in the entire protein (on the order of nanometers). This phenomenon is known as mechanical amplification <ref>Vale, R.D. and Milligan, R.A. (2000.) The way things move: looking under the hood of molecular motor proteins. Science 288(5463): 88-95.</ref>.
+In solution or in a free state, kinesin has <scene name='Sandbox_Reserved_473/Atp_binding_site/3'>ADP</scene> bound to each head or motor domain. Once kinesin attaches to a microtubule and changes its conformation slightly, ADP can be exchanged for high-energy ATP. This action causes the <scene name='Sandbox_Reserved_473/Neck/1'>neck linker</scene> to “zipper” into a binding pocket in the motor domain (near a structure called the <scene name='Sandbox_Reserved_473/Relay_helix/1'>relay helix</scene>). The zippering causes the second head of the kinesin to swing around and land on the microtubule ahead of the first head <ref name = "movie">Milligan, R. (2000.) An animated model for processive motility by conventional kinesin (movie). Retrieved from http://www.scripps.edu/milligan/research/movies/kinesin_text.html</ref>. The second head may reach the microtubule either by active movement, by simple diffusion, or by a combination of the two <ref name = "woehlke"/>. While the second head binds the microtubule, ATP hydrolysis occurs at the first head, releasing it from the microtubule. ATP hydrolysis also “unzippers” the neck linker from the relay helix, resetting the conformation for another reaction. It is remarkable that ATP binding and hydrolysis create tiny conformational changes in the active site (on the order of angstroms) that can lead to large overall conformational changes in the entire protein (on the order of nanometers). This phenomenon is known as mechanical amplification <ref>Vale, R.D. and Milligan, R.A. (2000.) The way things move: looking under the hood of molecular motor proteins. Science 288(5463): 88-95.</ref>.
 The reaction repeats over and over again as the kinesin binds and hydrolyzes one ATP for each 8-nanometer step it takes <ref name = "pdb">Goodsell, D. (2005.) Kinesin. RCSB Protein Data Bank. Retrieved from http://www.rcsb.org/pdb/101/motm.do?momID=64</ref>. Once bound to the microtubule, kinesin can take several steps without falling off, an ability known as processivity.