STRUCTURAL BASIS FOR AMEBOID MOTILITY IN NEMATODE SPERM

Cell locomotion in amoeboid nematode sperm is generated by the vectori al assembly and bundling of filaments of the major sperm protein (MSP) . MSP filaments are constructed from two helical subfilaments and here we describe the structure of putative MSP subfilament helices determi ned by X-ray crystallography at 3.3 Angstrom resolution. In addition t o establishing the interfaces involved in polymerization, this structu ral model shows that the MSP helices are constructed from dimers and h ave no overall polarity, suggesting that it is unlikely that molecular motors play a direct role in the generation of protrusive force in th ese amoeboid cells.