User:Jamie Abbott/Sandbox2: Difference between revisions
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=== Electrophilic Catalysis === | === Electrophilic Catalysis === | ||
The HisRS active site contains a highly conserved residue in the HisRS family, Arg259, that takes part in electrophilic catalysis for the adenylation reaction. This active site arginine residue is not present in other aaRS class II enzymes. As mentioned previously Arg259 and Arg113 are positioned to interact with the α-phosphate of ATP to assist in the adenylation reaction. Arg259 is positioned on the HisA loop to fix the α-carboxylate group of the histidine substrate as the <scene name='User:Jamie_Abbott/Sandbox2/His-r259/2'>attacking nucleophile</scene><ref>PMID: 9715912</ref>. Also, one ηN of the guanidinium group of Arg259 is positioned approximately 3Å from the α-phosphate of ATP while the other ηN hydrogen bonds with phenolic group of Tyr264. Thus, stabilization of the Tyr264 residue further enhances substrate binding allowing for the formation of a hydrogen bond to the Nδ of the histidine<ref name="aaRSbk" />. | The HisRS active site contains a highly conserved residue in the HisRS family, Arg259, that takes part in electrophilic catalysis for the adenylation reaction. This active site arginine residue is not present in other aaRS class II enzymes. As mentioned previously | ||
<scene name='User:Jamie_Abbott/Sandbox2/His-r259_and_113/1'>Arg259 and Arg113</scene> are positioned to interact with the α-phosphate of ATP to assist in the adenylation reaction. Arg259 is positioned on the HisA loop to fix the α-carboxylate group of the histidine substrate as the <scene name='User:Jamie_Abbott/Sandbox2/His-r259/2'>attacking nucleophile</scene><ref>PMID: 9715912</ref>. Also, one ηN of the guanidinium group of Arg259 is positioned approximately 3Å from the α-phosphate of ATP while the other ηN hydrogen bonds with phenolic group of Tyr264. Thus, stabilization of the Tyr264 residue further enhances substrate binding allowing for the formation of a hydrogen bond to the Nδ of the histidine<ref name="aaRSbk" />. | |||
