1h7e: Difference between revisions

[[Image:1h7e.gif|left|200px]]<br /><applet load="1h7e" size="350" color="white" frame="true" align="right" spinBox="true"  

The enzyme CMP-Kdo synthetase (CKS) catalyzes the activation of the sugar Kdo (2-keto-3-deoxy-manno-octonic acid) by forming a monophosphate diester. CKS is a pharmaceutical target because CMP-Kdo is used in the biosynthesis of lipopolysaccharides that are vital for Gram-negative bacteria. We have refined the structure of the unligated capsule-specific CKS from Escherichia coli at 1.8 A resolution (1 A=0.1 nm) and we have established the structures of its complexes with the substrate CTP, with CDP and CMP as well as with the product analog CMP-NeuAc (CMP-sialate) by X-ray diffraction analyses at resolutions between 2.1 A and 2.5 A. The N-terminal domains of the dimeric enzyme bind CTP in a peculiar nucleotide-binding fold, whereas the C-terminal domains form the dimer interface. The observed binding geometries together with the amino acid variabilities during evolution and the locations of a putative Mg(2+) and of a very strongly bound water molecule suggest a pathway for the catalysis. The N-terminal domain shows sequence homology with the CMP-NeuAc synthetases. Moreover, the chain fold and the substrate-binding position of CKS resemble those of other enzymes processing nucleotide-sugars.

1H7E is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Active as [http://en.wikipedia.org/wiki/3-deoxy-manno-octulosonate_cytidylyltransferase 3-deoxy-manno-octulosonate cytidylyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.7.7.38 2.7.7.38] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1H7E OCA].  

[[Category: Schulz, G E.]]

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