The three‐dimensional structure of notexin, a presynaptic neurotoxic phospholipase A2 at 2.0 Å resolution

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Abstract
The three-dimensional structure of notexin has been solved by molecular replacement methods. The structure has been refined at 2.0 Å resolution to a crystallographic R-value of 16.5% with good stereo-chemistry. The core of the protein is very similar to other phospholipase A2s (PLA2s) but several parts of the molecule are distinctly different. The most significant differences from PLA2s from bovine pancreas and rattlesnake occur in the stretches 56–80 and 85–89. Residue 69, which has been shown to be important for phospholipase binding, has a different conformation and different interactions than in other known PLA2s. The Cα positions for residues 86–88 differ by about 6 Å from both the bovine and the rattlesnake enzyme. The crystals contain no Ca2+ ions. Instead, a water molecule occupies the calcium site