Alpha crystallin: Difference between revisions

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Both subunits are polydisperse, oligomeric proteins that are made of flexible monomers with large surface areas. This means that they are very low molecular weight polymers made of a small number of repeat units ranging in various sizes. Based on their surrounding environment, their oligomeric properties will vary. Due to their oligomeric properties, each of these subunits is able to associate and form about 40 chain-long, large complexes in the shape of a sphere called oligomeric complexes. These complexes form when the monomers dimerize, causing the amino region and carboxyl regions of the alpha-crystallin to interact with residues from other corresponding regions of their neighboring subunits. These spheres are so large and oppositely charged that they repel and distribute themselves across the lens cells. When combined to create alpha-crystallin, the proteins exist as globular aggregates whose quaternary structure is believed to behave as a protein micelle. However, high-resolution data about the quaternary and tertiary structure of alpha-crystallin is unavailable, which is likely due to the polydisperse nature of alpha-crystallin. After 50 years of extensive study, the three-dimensional structure remains unknown because the protein is too large for NMR measurements and has yet to be obtained for X-ray studies.

In humans, both of these crystalline forms are coded for on different chromosomes. While they may be coded differently, they possess about 55% sequence homology between themselves. This means that they are structurally similar due to the evolutionary pathway and ancestral history that they both underwent. Despite their similar makeups, they do have unique features about them. For example, alpha-B crystallin is stress-inducible while alpha-A crystallin is not. This implies that alpha-B crystallin has a distinct role in the eye's lens.

Alpha-A crystallin is made of 173 amino acids arranged in <scene name='88/881544/Beta_sheet/1'>a beta sheet pattern</scene>. The molecular mass of the alpha-A subunit is 19.8 kDa, and the homooligomer weighs 660 kDa. On the other hand, Alpha-B crystallin has 165 amino acids arranged in seven beta-sheets, has a molecular mass of 20 kDa, and its homooligomer weight is 620 kDa. Together, the alpha-crystallin protein has four Zinc binding sites, all of which are in the same position as the four metal-binding sites. Within the crystallin is two tryptophan residues, Trp9 and Trp60, both of which can be found in the alpha-B crystallin subunit.

Alpha-A crystallin is made of 173 amino acids arranged in <scene name='88/881544/Beta_sheet/1'>a beta sheet pattern</scene>. The molecular mass of the alpha-A subunit is 19.8 kDa, and the homooligomer weighs 660 kDa. On the other hand, Alpha-B crystallin has 165 amino acids arranged in seven beta-sheets, has a molecular mass of 20 kDa, and its homooligomer weight is 620 kDa. Together, the alpha-crystallin protein has <scene name='88/881544/Zinc_and_zinc_binding_sites/1'>four Zinc binding sites</scene>, all of which are in the same position as the four metal-binding sites. Within the crystallin is two tryptophan residues, Trp9 and Trp60, both of which can be found in the alpha-B crystallin subunit.

Alpha crystallin: Difference between revisions

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 Both subunits are polydisperse, oligomeric proteins that are made of flexible monomers with large surface areas. This means that they are very low molecular weight polymers made of a small number of repeat units ranging in various sizes. Based on their surrounding environment, their oligomeric properties will vary. Due to their oligomeric properties, each of these subunits is able to associate and form about 40 chain-long, large complexes in the shape of a sphere called oligomeric complexes. These complexes form when the monomers dimerize, causing the amino region and carboxyl regions of the alpha-crystallin to interact with residues from other corresponding regions of their neighboring subunits. These spheres are so large and oppositely charged that they repel and distribute themselves across the lens cells. When combined to create alpha-crystallin, the proteins exist as globular aggregates whose quaternary structure is believed to behave as a protein micelle. However, high-resolution data about the quaternary and tertiary structure of alpha-crystallin is unavailable, which is likely due to the polydisperse nature of alpha-crystallin. After 50 years of extensive study, the three-dimensional structure remains unknown because the protein is too large for NMR measurements and has yet to be obtained for X-ray studies.
 In humans, both of these crystalline forms are coded for on different chromosomes. While they may be coded differently, they possess about 55% sequence homology between themselves. This means that they are structurally similar due to the evolutionary pathway and ancestral history that they both underwent. Despite their similar makeups, they do have unique features about them. For example, alpha-B crystallin is stress-inducible while alpha-A crystallin is not. This implies that alpha-B crystallin has a distinct role in the eye's lens.
-Alpha-A crystallin is made of 173 amino acids arranged in <scene name='88/881544/Beta_sheet/1'>a beta sheet pattern</scene>. The molecular mass of the alpha-A subunit is 19.8 kDa, and the homooligomer weighs 660 kDa. On the other hand, Alpha-B crystallin has 165 amino acids arranged in seven beta-sheets, has a molecular mass of 20 kDa, and its homooligomer weight is 620 kDa. Together, the alpha-crystallin protein has four Zinc binding sites, all of which are in the same position as the four metal-binding sites. Within the crystallin is two tryptophan residues, Trp9 and Trp60, both of which can be found in the alpha-B crystallin subunit.
+Alpha-A crystallin is made of 173 amino acids arranged in <scene name='88/881544/Beta_sheet/1'>a beta sheet pattern</scene>. The molecular mass of the alpha-A subunit is 19.8 kDa, and the homooligomer weighs 660 kDa. On the other hand, Alpha-B crystallin has 165 amino acids arranged in seven beta-sheets, has a molecular mass of 20 kDa, and its homooligomer weight is 620 kDa. Together, the alpha-crystallin protein has <scene name='88/881544/Zinc_and_zinc_binding_sites/1'>four Zinc binding sites</scene>, all of which are in the same position as the four metal-binding sites. Within the crystallin is two tryptophan residues, Trp9 and Trp60, both of which can be found in the alpha-B crystallin subunit.