Amoeboid sperm from Ascaris contain an unusual cytoskeleton, composed of major sperm protein (MSP). In spermatozoa MSP filaments are organized into fiber complexes that extend from the leading edge to the base of the pseudopod and flow rearward at the same rate as the cell crawls forward. The tight coupling between cytoskeletal flow and motility indicates a key role for the MSP cytoskeleton in locomotion. I have studied both the regulation and structure of the MSP filament system in Ascaris sperm. Changes in intracellular pH (pH$\sb{\rm i}$) are involved in controlling the assembly status of MSP in vivo. Spermatozoa established a pseudopodial pH gradient with pH$\sb{\rm i}$ 0.15 units higher at the leading edge, where fiber complexes assemble, than at the base where disassembly occurs. Agents that abolished this gradient, such as weak acids, caused the cell to stop crawling and the fiber complexes to disassemble. The correlation between elevated pH$\sb{\rm i}$ and MSP assembly and low pH$\sb{\rm i}$ and depolymerization also was observed in developing sperm, indicating that pH regulation of the cytoskeleton also occurs during spermatogenesis. To understand cytoskeletal dynamics in greater detail, I studied the structure of MSP polymers. Self-association of monomers into helical assemblies is an intrinsic property of MSP. This feature is clearly displayed in the number of polymorphic forms MSP assumes in vivo and in vitro. We have characterized 4 distinct assemblies--subfilaments, filaments, macrofibers, and fiber complexes. Individual filaments formed either in vivo or in vitro are composed of two subfilaments wrapping around each other. These filaments coil around one another to form larger helical assemblies, macrofibers in vitro and fiber complexes in vivo. Filaments do not require accessory proteins to interact. Self-association of MSP filaments into / helical superstructures may have important implications for the role of MSP in sperm motility. This property could allow the filaments to form fiber complexes without requiring accessory proteins and, thus, create a simple framework to propel locomotion. / Source: Dissertation Abstracts International, Volume: 54-12, Section: B, page: 6023. / Major Professor: Thomas Michael Roberts. / Thesis (Ph.D.)--The Florida State University, 1993.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_77073 |
| Contributors | King, Karen Lynne., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 108 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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