2a0f: Difference between revisions

[[Image:2a0f.gif|left|200px]]<br /><applet load="2a0f" size="350" color="white" frame="true" align="right" spinBox="true"  

Snapshots of the catalytic cycle of the allosteric enzyme aspartate transcarbamoylase have been obtained via X-ray crystallography. The enzyme in the high-activity high-affinity R state contains two catalytic chains in the asymmetric unit that are different. The active site in one chain is empty, while the active site in the other chain contains an analog of the first substrate to bind in the ordered mechanism of the reaction. Small angle X-ray scattering shows that once the enzyme is converted to the R state, by substrate binding, the enzyme remains in the R state until substrates are exhausted. Thus, this structure represents the active form of the enzyme trapped at two different stages in the catalytic cycle, before the substrates bind (or after the products are released), and after the first substrate binds. Opening and closing of the catalytic chain domains explains how the catalytic cycle occurs while the enzyme remains globally in the R-quaternary structure.

2A0F is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=ZN:'>ZN</scene> and <scene name='pdbligand=PCT:'>PCT</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Aspartate_carbamoyltransferase Aspartate carbamoyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.1.3.2 2.1.3.2] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2A0F OCA].  

[[Category: Cardia, J P.]]

[[Category: Dusinberre, K J.]]

[[Category: Kantrowitz, E R.]]

[[Category: Stieglitz, K A.]]

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