Buttery Shawnna M, Ekman Gail C, Seavy Margaret, Stewart Murray, Roberts Thomas M
Department of Biological Science, Florida State University, Tallahassee, Florida 32306, USA.
Mol Biol Cell. 2003 Dec;14(12):5082-8. doi: 10.1091/mbc.e03-04-0246. Epub 2003 Oct 17.
Although Ascaris sperm motility closely resembles that seen in many other types of crawling cells, the lamellipodial dynamics that drive movement result from modulation of a cytoskeleton based on the major sperm protein (MSP) rather than actin. The dynamics of the Ascaris sperm cytoskeleton can be studied in a cell-free in vitro system based on the movement of plasma membrane vesicles by fibers constructed from bundles of MSP filaments. In addition to ATP, MSP, and a plasma membrane protein, reconstitution of MSP motility in this cell-free extract requires cytosolic proteins that orchestrate the site-specific assembly and bundling of MSP filaments that generates locomotion. Here, we identify a fraction of cytosol that is comprised of a small number of proteins but contains all of the soluble components required to assemble fibers. We have purified two of these proteins, designated MSP fiber proteins (MFPs) 1 and 2 and demonstrated by immunolabeling that both are located in the MSP cytoskeleton in cells and in fibers. These proteins had reciprocal effects on fiber assembly in vitro: MFP1 decreased the rate of fiber growth, whereas MFP2 increased the growth rate.
尽管蛔虫精子的运动与许多其他类型的爬行细胞非常相似，但驱动运动的片状伪足动力学是由基于主要精子蛋白（MSP）而非肌动蛋白的细胞骨架调节产生的。蛔虫精子细胞骨架的动力学可以在无细胞体外系统中进行研究，该系统基于由MSP细丝束构成的纤维对质膜囊泡的运动。除了ATP、MSP和一种质膜蛋白外，在这种无细胞提取物中重建MSP运动还需要胞质蛋白，这些蛋白协调MSP细丝的位点特异性组装和成束，从而产生运动。在这里，我们鉴定出一部分胞质溶胶，它由少量蛋白质组成，但包含组装纤维所需的所有可溶性成分。我们纯化了其中两种蛋白质，命名为MSP纤维蛋白（MFP）1和2，并通过免疫标记证明它们都位于细胞和纤维中的MSP细胞骨架中。这些蛋白质在体外对纤维组装有相反的作用：MFP1降低了纤维生长速率，而MFP2提高了生长速率。
