Sandbox Reserved 479: Difference between revisions
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==Structure== | ==Structure== | ||
Myosin is a 520 kDa hexamer, or a '''hexa-oligomer''' (6 subunit) structure. It is comprised of two heavy chains (weighing 220 kDa each) and 4 light chains (weighing 20 kDa each).<ref name="CHEM43">[http://www.cs.stedwards.edu/chem/Chemistry/CHEM43/CHEM43/Myosin/STRUCT~1.HTM]</ref> The hexamer's 2 identical heavy chains connected via the coiled coil structure, and each containing a regulatory and essential light chain (total of 4). The 2-D structure below of myosin II shows 7 stranded <scene name='Sandbox_Reserved_479/2mys_beta_sheet/2'>beta sheet</scene> (Jmol) and the ATP-binding site between the middle and N-terminal of the protein. The C-terminal contains the light chains (regulatory domain) and acts as the lever arm to enhance the converter domain's rotational movements.<ref name="sampath">[http://www.sampath.koppole.com/research.htm]</ref> | Myosin is a 520 kDa hexamer, or a '''hexa-oligomer''' (6 subunit) structure. It is comprised of two heavy chains (weighing 220 kDa each) and 4 light chains (weighing 20 kDa each).<ref name="CHEM43">[http://www.cs.stedwards.edu/chem/Chemistry/CHEM43/CHEM43/Myosin/STRUCT~1.HTM]</ref> The hexamer's 2 identical heavy chains connected via the coiled coil structure, and each containing a regulatory and essential light chain (total of 4). The 2-D structure below of myosin II head shows 7 stranded <scene name='Sandbox_Reserved_479/2mys_beta_sheet/2'>beta sheet</scene> (Jmol) and the ATP-binding site between the middle and N-terminal of the protein. The C-terminal contains the light chains (regulatory domain) and acts as the lever arm to enhance the converter domain's rotational movements.<ref name="sampath">[http://www.sampath.koppole.com/research.htm]</ref> | ||
[[Image:Mds1.png]] | [[Image:Mds1.png]] | ||
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====X-Ray Crystallography and Scattering==== | ====X-Ray Crystallography and Scattering==== | ||
It was not until recently that crystal structures could be used to analyze myosin and it's role in the actinomysin chemomechanical cycle. X-ray diffraction studies have been conducted on whole muscles and muscle fibers to learn how structural changes promote and facilitate motor activity. | It was not until recently that crystal structures could be used to analyze myosin and it's role in the actinomysin chemomechanical cycle. X-ray diffraction studies have been conducted on whole muscles and muscle fibers to learn how structural changes promote and facilitate motor activity. Modern synchrotron radiation sources allow us to study myosin at the molecular level under near-physiological conditions. Muscle cells exhibit low scattering power in X-ray images, however, so a clear crystalline structure cannot not form. A flat detector is needed because reflections are concentrated in the low angle regions. Snychrotron radiation generates a monochromatic X-ray breams of diameter 0.2-0.3 mm, similar to that of the muscle fiber, and making high resolution images and video of a single muscle cell possible via x-ray scattering patterns. New technology using snychrotron radiation and 2 dimensional detectors will allow researchers to gain even more insight into the structure of myosin and it's interaction with actin in unique time and spatial resolution.<ref name="Koubassova">PMID: 22339600</ref> | ||
==Interaction with Actin== | ==Interaction with Actin== | ||
[[Image:actinandmyosin.png]] | [[Image:actinandmyosin.png]] | ||
==Mechanism of Action== | Myosin disassociates and binds to actin via the hydrolysis of ATP into ADP and Pi. The force behind a muscle contraction is due to the swinging lever arm (myosin).<ref name="esrf">[http://www.esrf.eu/UsersAndScience/Publications/Highlights/2003/MX/MX03]</ref> | ||
===Mechanism of Action=== | |||
Myosin plays a role in the universal mechanism known as the actinomysin chemomechanical cycle. Actin binds and releases myosin, causing the myosin lever to interact and relax in a cyclic manner.<ref name="legacy">[http://legacy.owensboro.kctcs.edu/gcaplan/anat/notes/api%20notes%20j%20%20muscle%20contraction.htm]</ref> | Myosin plays a role in the universal mechanism known as the actinomysin chemomechanical cycle. Actin binds and releases myosin, causing the myosin lever to interact and relax in a cyclic manner.<ref name="legacy">[http://legacy.owensboro.kctcs.edu/gcaplan/anat/notes/api%20notes%20j%20%20muscle%20contraction.htm]</ref> | ||
