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Structural basis for amoeboid motility in nematode sperm
T L Bullock1, A J McCoy, H M Kent
1MRC Laboratory of Molecular Biology, Cambridge, UK.
Abstract:
Cell locomotion in amoeboid nematode sperm is generated by the vectorial 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 determined by X-ray crystallography at 3.3 A resolution. In addition to establishing the interfaces involved in polymerization, this structural model shows that the MSP helices are constructed from dimers and have no overall polarity, suggesting that it is unlikely that molecular motors play a direct role in the generation of protrusive force in these amoeboid cells.
Insights
Amoeboid sperm locomotion relies on major sperm protein (MSP) filament assembly. Structural analysis reveals MSP helices lack polarity, suggesting motors are not directly involved in force generation.
Area of Science:
- Cell biology
- Biochemistry
- Structural biology
Background:
- Amoeboid cell movement, particularly in nematode sperm, is driven by the assembly and bundling of major sperm protein (MSP) filaments.
- Understanding the structural basis of MSP filament formation is crucial for elucidating the mechanism of cell locomotion.
Purpose of the Study:
- To determine the three-dimensional structure of putative major sperm protein (MSP) subfilament helices.
- To identify the interfaces involved in MSP polymerization.
- To investigate the role of molecular motors in amoeboid cell protrusive force generation.
Main Methods:
- X-ray crystallography was employed to determine the structure of MSP subfilament helices.
- High-resolution structural analysis was performed at 3.3 Å resolution.
Main Results:
- A structural model of MSP subfilament helices was established.
- The interfaces critical for MSP polymerization were identified.
- The MSP helices were found to be constructed from dimers.
- The MSP helices exhibit no overall polarity.
Conclusions:
- The structural findings suggest that molecular motors are unlikely to directly generate protrusive force in amoeboid cells.
- The polarity of MSP helices does not appear to be a factor in force generation during cell locomotion.
- This study provides key insights into the structural organization of MSP filaments and their role in cell motility.