Structure analysis of endosialidase NF at 0.98 Å resolution

Endosialidase NF (endoNF) is a bacteriophage‐derived endosialidase that specifically degrades α‐2,8‐linked polysialic acid. The structure of a new crystal form of endoNF in complex with sialic acid has been refined at 0.98 Å resolution. The 210 kDa homotrimeric multi‐domain enzyme displays outstanding stability and resistance to SDS. Even at atomic resolution, only a minor fraction of side chains possess alternative conformations. However, multiple conformations of an active‐site residue imply that it has an important catalytic function in the cleavage mechanism of polysialic acid.