RNase A: Difference between revisions

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For a full list of protein structures related to RNase A, see [http://www.proteopedia.org/wiki/index.php/Category:Pancreatic_ribonuclease Pancreatic Ribonucleases].

=='''Ribonuclease A Catalysis'''==

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==='''Acid Base Catalysis by RNase A'''===

RNase A catalyzes the cleavage of the Phosphodiester bonds in two steps: the formation of the pentavalent phosphate transition state and subsequent degradation of the 2’3’ cyclic phosphate intermediate using three main catalytic residues (<scene name='Sandbox_Reserved_193/His12_lys41_his119/1'>His12, Lys41, and His119</scene>). An important part of the reaction is the ability of histidine (His 12 and His119) to both accept and donate electrons, allowing these histidine to be an acid or a base, making the reaction pH dependent <ref name="Raines" />.

RNase A catalyzes the cleavage of the Phosphodiester bonds in two steps: the formation of the pentavalent phosphate transition state and subsequent degradation of the 2’3’ cyclic phosphate intermediate using three main catalytic residues (<scene name='Sandbox_Reserved_193/His12_lys41_his119/1'>His12, Lys41, and His119</scene> and <scene name='Sandbox_Reserved_194/His12_lys41_his119/1'>His12, Lys41, and His119 with substrate present</scene>). An important part of the reaction is the ability of histidine (His 12 and His119) to both accept and donate electrons, allowing these histidine to be an acid or a base, making the reaction pH dependent <ref name="Raines" />.

RNA hydrolysis begins when <scene name='Sandbox_Reserved_193/His12a_a/1'>His12</scene> abstracts a proton from the 2’ OH group on RNA; thus, assisting in the nucleophilic attack of the 2’ oxygen on the electrophilic phosphorus atom. A transition state is then formed, having a pentavalent phosphate, which is stabilized by the positively charged amino group of <scene name='Sandbox_Reserved_193/Lys41a_a/1'>Lys41</scene> and the main chain amide nitrogen of Phe120. <scene name='Sandbox_Reserved_193/His119a_a/1'>His119</scene> then protonates the 5' oxygen on the ribose ring and the transition state falls to form a 2’3’cyclic phosphate intermediate <ref name="Raines" />.

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@@ Line 12: / Line 12: @@
 For a full list of protein structures related to RNase A, see [http://www.proteopedia.org/wiki/index.php/Category:Pancreatic_ribonuclease Pancreatic Ribonucleases].
 =='''Ribonuclease A Catalysis'''==
@@ Line 30: / Line 29: @@
 ==='''Acid Base Catalysis by RNase A'''===
-RNase A catalyzes the cleavage of the Phosphodiester bonds in two steps: the formation of the pentavalent phosphate transition state and subsequent degradation of the 2’3’ cyclic phosphate intermediate using three main catalytic residues (<scene name='Sandbox_Reserved_193/His12_lys41_his119/1'>His12, Lys41, and His119</scene>). An important part of the reaction is the ability of histidine (His 12 and His119) to both accept and donate electrons, allowing these histidine to be an acid or a base, making the reaction pH dependent <ref name="Raines" />.
+RNase A catalyzes the cleavage of the Phosphodiester bonds in two steps: the formation of the pentavalent phosphate transition state and subsequent degradation of the 2’3’ cyclic phosphate intermediate using three main catalytic residues (<scene name='Sandbox_Reserved_193/His12_lys41_his119/1'>His12, Lys41, and His119</scene> and <scene name='Sandbox_Reserved_194/His12_lys41_his119/1'>His12, Lys41, and His119 with substrate present</scene>). An important part of the reaction is the ability of histidine (His 12 and His119) to both accept and donate electrons, allowing these histidine to be an acid or a base, making the reaction pH dependent <ref name="Raines" />.
 RNA hydrolysis begins when <scene name='Sandbox_Reserved_193/His12a_a/1'>His12</scene> abstracts a proton from the 2’ OH group on RNA; thus, assisting in the nucleophilic attack of the 2’ oxygen on the electrophilic phosphorus atom. A transition state is then formed, having a pentavalent phosphate, which is stabilized by the positively charged amino group of <scene name='Sandbox_Reserved_193/Lys41a_a/1'>Lys41</scene> and the main chain amide nitrogen of Phe120. <scene name='Sandbox_Reserved_193/His119a_a/1'>His119</scene> then protonates the 5' oxygen on the ribose ring and the transition state falls to form a 2’3’cyclic phosphate intermediate <ref name="Raines" />.