Three-dimensional structure of neurotoxin-1 from Naja naja oxiana venom at 1.9 A resolution.

Neurotoxin-1 from Naja naja oxiana venom (NTX-1) has been crystallized by vapor diffusion in sitting drops. The crystals have cell dimensions of a = 25.2 A, b = 75.6 A, c = 35.9 A, and are in space group P2(1)2(1)2(1). Three-dimensional data to 1.9 A have been recorded by a Syntex P2(1) automatic diffractometer. The atomic structure of the toxin has been determined by molecular replacement using the alpha-cobratoxin (alpha-CTX) as the search model. The position of 534 non-hydrogen protein atoms have been determined. The model contains 65 water molecules. Refinement has led to an R-factor of 19.3% at 1.9 A resolution. The secondary and tertiary structures of NTX-1 have been analyzed and a comparison with structure of the alpha-CTX has been made.