Bird Flu Neuraminidase type N9 native structure

Currently a new strain of avian influenza is causing concern for human health. This H7N9 strain has a coat containing N9 neuraminidase. It is timely to place the native structure of this enzyme in the Gallery (click here for link). While adding N9 neuraminidase to the Gallery, I noticed that the N2 neuraminidase listed there was not displaying. I have corrected that error and now all three neuraminidases on display can be compared. Note that the details of the native structures of these neuraminidases and 8 others were published on this blog in the post of April 14 2007. Careful inspection of the native structures of N9 and N2 neuraminidases shows that the differences are minute although the amino acid sequences differ significantly. This reflects the fact that both proteins perform the same tasks in almost identical environments. In contrast, the crystal structures clearly differ in subunit orientation. It is an emerging fact that crystal quaternary structures are much more diverse than native quaternary structures, presumably because crystal quaternary structures are artefacts of the interaction of surface charges with water in the crystal phase. The relationship between native structure and function, together with the phenomena determining crystal structures were discussed on this blog in the two posts of December 9 2011.