Sandbox 171: Difference between revisions
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{{STRUCTURE_2mys| PDB=2mys| Scene =Sandbox_171/Newscene/1'>active site }} | {{STRUCTURE_2mys| PDB=2mys| Scene =Sandbox_171/Newscene/1'>active site }} | ||
= | ==Overview== | ||
Myosin is one of three major classes of molecular motors: myosin, dynein, and kinesin. As the most abundant of these proteins myosin plays a structural and enzymatic role in muscle contraction and intracellular motility. Myosin was first discovered in muscle in the 19th century. <ref name="Spudich">PMID: 8824453 </ref> | Myosin is one of three major classes of molecular motors: myosin, dynein, and kinesin. As the most abundant of these proteins myosin plays a structural and enzymatic role in muscle contraction and intracellular motility. Myosin was first discovered in muscle in the 19th century. <ref name="Spudich">PMID: 8824453 </ref> | ||
===Crystallization and X-ray diffraction=== | |||
Myosin is found in abundance, therefore can be prepared in gram quantities. <ref name="Rayment">PMID: 8316857</ref> For nearly 30 years the myosin head was resistant to crystallization yet by 1993 researchers discovered a mechanism to obtain x-ray quality crystals. <ref name="Rayment" /> The process modified the protein by reductive methylation. <ref name="Rayment" /> X-ray data was used to determine the structure. <ref name="Rayment" /> | |||
==Structure== | ==Structure== | ||
Myosin has a molecular size of approximately 520 kilodaltons, with two 220 kD heavy chains and two pairs of light chains which vary in size. <ref name="Rayment" | Myosin has a molecular size of approximately 520 kilodaltons, with two 220 kD heavy chains and two pairs of light chains which vary in size.<ref name="Rayment" /> The molecule is asymmetric, having a long tail and two globular heads. <ref name="Rayment" /> Each heavy chains composes the bulk of one of the globular heads. <ref name="Rayment" /> Subfragment-1(S1) also termed the myosin head consists of ATP, actin, and two light chain binding sites.<ref name="Rayment" /> Each globular head has a heavy chain and two light chains for a combined molecular size of about 130 kD. <ref name="Rayment" /> | ||
The myosin head is assymetrical with a length of 165 Angstroms and 65 Angstroms in width, with a total thickness of about 40 Angstroms. <ref name="Rayment" /> About 48% of the amino acid residues in the myosin head are dominated by α helices. <ref name="Rayment" /> One long α helix of about 85 Angstroms stretches from the thick part of the myosin head to the COOH-terminus of the heavy chain. <ref name="Rayment" /> This particular helix forms the light chain binding region on the heavy chain. <ref name="Rayment" /> | |||
[[Image:Myosin_head.gif|thumb|alt=Alt text|Myosin head]] | [[Image:Myosin_head.gif|thumb|alt=Alt text|Myosin head]] | ||
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Click the link to access DNAtube video "A Moving Myosin Motor Protein" | Click the link to access DNAtube video "A Moving Myosin Motor Protein" | ||
http://www.dnatube.com/video/389/A-Moving-Myosin-Motor-Protein-myosin-actin-interaction | http://www.dnatube.com/video/389/A-Moving-Myosin-Motor-Protein-myosin-actin-interaction | ||