1qwj: Difference between revisions

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

Sialic acids are activated by CMP-5-N-acetylneuraminic acid synthetase prior to their transfer onto oligo- or polysaccharides. Here, we present the crystal structure of the N-terminal catalytically active domain of the murine 5-N-acetylneuraminic acid synthetase in complex with the reaction product. In contrast to the previously solved structure of 5-N-acetylneuraminic acid synthetase from Neisseria meningitidis and the related CMP-KDO-synthetase of Escherichia coli, the murine enzyme is a tetramer, which was observed with the active sites closed. In this conformation a loop is shifted by 6A towards the active site and thus an essential arginine residue can participate in catalysis. Furthermore, a network of intermolecular salt-bridges and hydrogen bonds in the dimer as well as hydrophobic interfaces between two dimers indicate a cooperative behaviour of the enzyme. In addition, a complex regulation of the enzyme activity is proposed that includes phosphorylation and dephosphorylation.

1QWJ is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Mus_musculus Mus musculus] with <scene name='pdbligand=NCC:'>NCC</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/N-acylneuraminate_cytidylyltransferase N-acylneuraminate cytidylyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.7.7.43 2.7.7.43] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1QWJ OCA].  

[[Category: Kaiser, J T.]]

[[Category: Muenster-Kuehnel, A K.]]

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