1w0p: Difference between revisions

Vibrio cholerae neuraminidase (VCNA) plays a significant role in the, pathogenesis of cholera by removing sialic acid from higher order, gangliosides to unmask GM1, the receptor for cholera toxin. We previously, showed that the structure of VCNA is composed of a central beta-propeller, catalytic domain flanked by two lectin-like domains; however the nature of, the carbohydrates recognized by these lectin domains has remained unknown., We present here structures of the enzyme in complex with two substrates, alpha-2,3-sialyllactose and alpha-2,6-sialyllactose. Both substrate, complexes reveal the alpha-anomer of N-acetylneuraminic acid (Neu5Ac), bound to the N-terminal lectin domain, thereby revealing the role of this, domain. The large number of interactions suggest a relatively high binding, affinity for sialic acid, which was confirmed by calorimetry, which gave a, Kd approximately 30 microm. Saturation transfer difference NMR using a, non-hydrolyzable substrate, Neu5,9Ac2-2-S-(alpha-2,6)-GlcNAcbeta1Me, was, also used to map the ligand interactions at the VCNA lectin binding site., It is well known that VCNA can hydrolyze both alpha-2,3- and, alpha-2,6-linked sialic acid substrates. In this study using, alpha-2,3-sialyllactose co-crystallized with VCNA it was revealed that the, inhibitor 2-deoxy-2,3-didehydro-N-acetylneuraminic acid (Neu5Ac2en) was, bound at the catalytic site. This observation supports the notion that, VCNA can produce its own inhibitor and has been further confirmed by 1H, NMR analysis. The discovery of the sialic acid binding site in the, N-lectin-like domain suggests that this might help target VCNA to sialic, acid-rich environments, thereby enhancing the catalytic efficiency of the, enzyme.

1W0P is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Vibrio_cholerae Vibrio cholerae] with SIA, CA, TRS and GOL as [http://en.wikipedia.org/wiki/ligands ligands]. Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1W0P OCA].  

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