Sialidase Micromonospora viridifaciens

Watson JN, Newstead S, Narine AA, Taylor G, Bennet AJ (2005) Two nucleophilic mutants of the Micromonospora viridifaciens sialidase operate with retention of configuration by two different mechanisms. Chembiochem 6 1999-2004... 

Very remarkably, site-directed mutagenesis of the supposedly nucleophilic tyrosine of the GH 33 sialidase from Micromonospora viridifaciens yields enzymes which still work, and some of them act with inversion, rather than retention. A detailed examination of the inverting Y 370G mutant revealed that the hole left by removal of the tyrosine side-chain was now filled with water molecules surprisingly, the effect of removing the nucleophilic tyrosine... 

Evidence for a horizontal sialidase gene transfer between bacteria has been obtained by comparison of the similarities of bacterial sialidases so far sequenced [246,660,768,799]. It was found that some of the sialidases are related in accordance with the phylogenetic distances of their producers, e.g. Micromonospora viridifaciens and Actinomyces viscosus... 

The crystal structures of two representative small sialidases, with molecular weights around 40 kDa, have been determined one from Salmonella typhimurium [17] and one from Micromonospora viridifaciens [I8j. These reveal the same P-propeller fold seen in the influenza virus neuraminidase (Figure 2), despite having no sequence similarity to the viral enzyme, and not containing any disulphide bonds in contrast to the seven conserved disulfides in the viral enzyme. 

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