User:John S. de Banzie/Sandbox 2

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==Carboxypeptidase A with "Substrate" Bound==
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==Carboxypeptidase A with Substrate==
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<StructureSection load='3cpa' size='400' side='right' caption='Carboxypeptidase A complexed with dipeptide in the active site, [[3cpa]]' scene='59/590622/3cpaspacefill/2'>
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<StructureSection load='3cpa' size='400' side='right' caption='Carboxypeptidase A with the dipeptide Gly-Tyr in the active site, [[3cpa]]' scene='59/590622/3cpaspacefill/2'>
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Carboxypeptidase A catalyses the release of the C-terminal amino acid from a polypeptide chain. The initial image shows carboxypeptidase with a dipeptide (green) bound in the active site.
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Carboxypeptidase A catalyses the release of the C-terminal amino acid from a polypeptide chain. The initial image shows carboxypeptidase with a dipeptide (green) in the active site.
The enzyme has <scene name='59/590622/3cpacartoon/1'>mixed secondary structure</scene>. A zinc ion (violet) is present. The ion is involved in binding and catalysis.
The enzyme has <scene name='59/590622/3cpacartoon/1'>mixed secondary structure</scene>. A zinc ion (violet) is present. The ion is involved in binding and catalysis.
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Substrate binding involves three interactions between the substrate and the active site.
Substrate binding involves three interactions between the substrate and the active site.
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1. <scene name='59/590622/1zlhbindone/1'>Between the carbonyl group of the penultimate residue in the substrate and the zinc ion and an arginyl residue in the enzyme</scene>.
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1. <scene name='59/590622/3cpabindone/1'>Between the carbonyl group of the penultimate residue in the substrate and the zinc ion and an arginyl residue in the enzyme</scene>.
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2. <scene name='59/590622/1zlhbindtwo/1'>Between the C-terminal carboxyl group and asparaginyl, arginyl, and tyrosyl residues in the enzyme</scene>.
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2. <scene name='59/590622/3cpabindtwo/1'>Between the C-terminal carboxyl group and asparaginyl, arginyl, and tyrosyl residues in the enzyme</scene>.
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3. <scene name='59/590622/1zlhbindthree/1'>Between the C-terminal R group and a hydrophobic pocket in the enzyme</scene>.
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3. <scene name='59/590622/3cpabindthree/1'>Between the C-terminal R group and a hydrophobic pocket in the enzyme</scene>.
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Catalysis involves <scene name='59/590622/1zlhcatalysis/1'>electron withdrawal from the carbonyl of the penultimate residue by the zinc ion and an arginyl residue, and nucleophilic attack on that same group by a glutamyl residue</scene>.
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Catalysis involves <scene name='59/590622/3cpacatalysis/1'>electron withdrawal from the carbonyl of the penultimate residue by the zinc ion and an arginyl residue, and nucleophilic attack on that same group by a glutamyl residue</scene>.
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(The tetrapeptide is actually the C-terminus of a protein that inhibits carboxypeptidase A. This portion of the inhibitor mimics the binding of substrate to the active site.)
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(The substrate remained intact because Gly-Tyr is hydrolyzed very slowly and because X-ray crystallography was carried out at -9° C.)
</StructureSection>
</StructureSection>
== References ==
== References ==
<references/>
<references/>

Revision as of 13:57, 13 June 2014

Carboxypeptidase A with Substrate

Carboxypeptidase A with the dipeptide Gly-Tyr in the active site, 3cpa

Drag the structure with the mouse to rotate

References

Proteopedia Page Contributors and Editors (what is this?)

John S. de Banzie

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