Sandbox 156: Difference between revisions
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==Structure== | ==Structure== | ||
<applet load='4CLA' size='300' frame='true' align='right' caption='' /> | |||
The general structure of CAT III is dominated by a six stranded antiparallel <scene name='Sandbox_156/Scene_4/4'>β-sheet</scene> and 5 <scene name='Sandbox_156/Scene_4/3'>α-helices</scene> stacked against the ends and face of the protein, forming a structure known as an "open-faced sandwhich"<ref>PMID: 3288984</ref>. Three identical monomers associate to form the trimeric protein with two <scene name='Sandbox_156/Scene_7/1'>cobalt</scene> ions acting as cofactors. | The general structure of CAT III is dominated by a six stranded antiparallel <scene name='Sandbox_156/Scene_4/4'>β-sheet</scene> and 5 <scene name='Sandbox_156/Scene_4/3'>α-helices</scene> stacked against the ends and face of the protein, forming a structure known as an "open-faced sandwhich"<ref>PMID: 3288984</ref>. Three identical monomers associate to form the trimeric protein with two <scene name='Sandbox_156/Scene_7/1'>cobalt</scene> ions acting as cofactors. | ||
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===The Active Site=== | ===The Active Site=== | ||
The active site, also the chloramphenicol binding site, catalyzes sequential acetylations of the chloramphenicol molecule. This is initiated by the deprotonation of the 3-hydroxyl of chloramphenicol by <scene name='Sandbox_156/Scene_two/1'>His-195</scene><ref>PMID:2015231</ref>. Numerous hydrogen bonds are present and, most importantly, an interaction between the benzene ring of the <scene name='Sandbox_156/Scene_4/1'>Tyr-25</scene> residue and the imidazole ring. This van der Waals contact may help stabilize side-chain orientations, promoting specificity in the reaction. The acetyl group is already properly positioned after tunneling, and reacts readily without any major structural changes<ref>PMID: 3288984</ref>. | |||
{{STRUCTURE_4CLA | PDB=4CLA | Scene=Sandbox_156/Scene_1/1}} | |||
<scene name='Sandbox_156/Scene_1/1'>binding site?</scene> | <scene name='Sandbox_156/Scene_1/1'>binding site?</scene> | ||
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