Crystallization of the motile major sperm protein (MSP) of the nematode Ascaris suum.

We have obtained orthorhombic crystals (space group P2(1)2(1)2(1), a = 72 A, b = 78 A, c = 452 A) of the major cytoskeletal protein associated with the amoeboid motility of Ascaris sperm. These crystals diffract past 3.5 A and appear to be constructed from arrays of helical fibres of the major sperm protein. The fibres within the crystals appear to be closely analogous to those seen in vitro and in vivo.