Sandbox Reserved 192: Difference between revisions
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<Structure load='7RSA' size='400' frame='true' align='right' caption='RNase A' scene='Sandbox_Reserved_192/Blue_ribonuclease/1' /> | <Structure load='7RSA' size='400' frame='true' align='right' caption='RNase A' scene='Sandbox_Reserved_192/Blue_ribonuclease/1' /> | ||
== '''Introduction''' == | == '''Introduction''' == | ||
[[Image: | [[Image:BOOBS.jpg|thumb|left|325px|Highlighted here is the kidney bean shape of RNase A with the active site located within the cleft..]] | ||
Ribonucleases [http://en.wikipedia.org/wiki/Ribonucleases] or RNA depolymerases are enzymes that catalyze RNA degradation. Ribonucleases are most commonly found in the pancreas because of their ability to digest large amounts of RNA excreted by the stomach. The pancreas in ruminants, such as cows, have especially high amounts of ribonucleases in order to process nutrients from cellulose based plants. One such ribonuclease, ribonuclease A or RNase A from cows, has been thoroughly studied due to its prevalence and structure. | Ribonucleases [http://en.wikipedia.org/wiki/Ribonucleases] or RNA depolymerases are enzymes that catalyze RNA degradation. Ribonucleases are most commonly found in the pancreas because of their ability to digest large amounts of RNA excreted by the stomach. The pancreas in ruminants, such as cows, have especially high amounts of ribonucleases in order to process nutrients from cellulose based plants. One such ribonuclease, ribonuclease A or RNase A from cows, has been thoroughly studied due to its prevalence and structure. | ||
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=='''Structure'''== | =='''Structure'''== | ||
RNase A is made up of a single polypeptide chain of 124 residues. Of the 20 natural amino acids, RNase A possesses 19 of them, excluding tryptophan. This single polypeptide chain is cross-linked internally by four <scene name='Sandbox_Reserved_192/Disulfide_linkages/3'>disulfide linkages</scene>, which contribute to the stability of RNase A. Long four-stranded anti-parallel <scene name='Sandbox_Reserved_192/Beta_sheet/ | RNase A is made up of a single polypeptide chain of 124 residues. Of the 20 natural amino acids, RNase A possesses 19 of them, excluding tryptophan. This single polypeptide chain is cross-linked internally by four <scene name='Sandbox_Reserved_192/Disulfide_linkages/3'>disulfide linkages</scene>, which contribute to the stability of RNase A. Long four-stranded anti-parallel <scene name='Sandbox_Reserved_192/Beta_sheet/3'>ß-sheets</scene> and three short <scene name='Sandbox_Reserved_192/Alpha_helices/1'>α-helices</scene> make up the <scene name='Sandbox_Reserved_192/Secondary_structure/1'>secondary structure</scene> of RNase A. RNase A is in the shape of a kidney, with the active-site residues located within the cleft. <scene name='Sandbox_Reserved_192/Active_site/1'>Active site</scene> residues <scene name='Sandbox_Reserved_192/Lysine_41/1'>Lys41</scene> and <scene name='Sandbox_Reserved_192/His_12/1'>His12</scene> and <scene name='Sandbox_Reserved_192/Histidine_119/1'>His119</scene> aid in catalysis for the enzyme. Lys41 has been found to stabilize the negative charge in the transition state, while His12 likely acts as a base in catalysis and His119 likely acts as an acid in catalysis. Catalytic residues are shown together <scene name='Sandbox_Reserved_192/Catalytic_residues/1'>here</scene>. The amino acid sequence determines the three-dimensional structure of RNase A based on side-chain interactions. | ||
=='''History'''== | =='''History'''== | ||
