Sandbox Reserved 479: Difference between revisions
From Proteopedia
Jump to navigationJump to search
No edit summary |
No edit summary |
||
| Line 19: | Line 19: | ||
The actin-binding, <scene name='Sandbox_Reserved_479/2mys_active_site/1'>catalytic site</scene> of myosin is known as S1 (subfragment 1). This is the amino-terminal globular head portion of the myosin molecule. The S1 head is divided into three subdomains: the NH2-terminal 25 kDa region, a central 50 kDa region, and the COOH-terminal 20 kDa region. Further analysis of the S1 active site of myosin suggests that the γ-phosphate (of ATP) binds near the apex of the 50 kDa cleft. It is believed to be a region critical to function, because of the presence of evolutionarily conserved residues along the central cleft.<ref name="Ruppel" /> The actin-binding site and nucleotide-binding site, although dominated by alpha-helices, also contains a straightened section with two cysteine residues. The can form a disulfide bond in the presence of a nucleotide that prevents ADP from leaving the active site.<ref name="CHEM43" /> | The actin-binding, <scene name='Sandbox_Reserved_479/2mys_active_site/1'>catalytic site</scene> of myosin is known as S1 (subfragment 1). This is the amino-terminal globular head portion of the myosin molecule. The S1 head is divided into three subdomains: the NH2-terminal 25 kDa region, a central 50 kDa region, and the COOH-terminal 20 kDa region. Further analysis of the S1 active site of myosin suggests that the γ-phosphate (of ATP) binds near the apex of the 50 kDa cleft. It is believed to be a region critical to function, because of the presence of evolutionarily conserved residues along the central cleft.<ref name="Ruppel" /> The actin-binding site and nucleotide-binding site, although dominated by alpha-helices, also contains a straightened section with two cysteine residues. The can form a disulfide bond in the presence of a nucleotide that prevents ADP from leaving the active site.<ref name="CHEM43" /> | ||
====X-Ray Crystallography and | ====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. Movement of myosin was analyzed under near physiological conditions using modern synchrotron radiation sources. Structural alterations were created through use of unique time and spatial resolution. Muscle cells exhibit low scattering power in X-ray images, 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.<ref name="Koubassova">PMID: 22339600</ref> | 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. Movement of myosin was analyzed under near physiological conditions using modern synchrotron radiation sources. Structural alterations were created through use of unique time and spatial resolution. Muscle cells exhibit low scattering power in X-ray images, 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.<ref name="Koubassova">PMID: 22339600</ref> | ||
| Line 36: | Line 36: | ||
==Medical Implications and Possible Applications== | ==Medical Implications and Possible Applications== | ||
The discovery of myosin structure served as a crucial component in understanding the causes of many health related problems. Dysfunctional myosin mutations have been linked to hypertrophy in the heart. The heart enlarges to compensate for inadequate cardiac muscle contractions and consequent poor blood circulation. Also, blood platelet contractile protein aggregation and secretion is impeded by faulty myosin in patients suffering from idiopathic scoliosis. A defect in the less-well known myosin VIIA causes Usher 1B syndrome; causing a loss of sight and hearing impairments. Further research will hopefully give more insight into the unknown causes of other diseases and disorders linked to myosin protein mutations.<ref name="CHEM43" /> | The discovery of myosin structure served as a crucial component in understanding the causes of many health related problems. Dysfunctional myosin mutations have been linked to hypertrophy in the heart. The power strokes are weaker, making muscle contractions less effective. The heart enlarges to compensate for inadequate cardiac muscle contractions and consequent poor blood circulation. Also, blood platelet contractile protein aggregation and secretion is impeded by faulty myosin in patients suffering from idiopathic scoliosis. A defect in the less-well known myosin VIIA causes Usher 1B syndrome; causing a loss of sight and hearing impairments. Further research will hopefully give more insight into the unknown causes of other diseases and disorders linked to myosin protein mutations.<ref name="CHEM43" /> | ||
==References== | ==References== | ||
<references/> | <references/> | ||
