Dissection of the Ascaris sperm motility machinery identifies key proteins involved in major sperm protein-based amoeboid locomotion.
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.
Buttery
Shawnna M
SM
Department of Biological Science, Florida State University, Tallahassee, Florida 32306, USA.
Ekman
Gail C
GC
Seavy
Margaret
M
Stewart
Murray
M
Roberts
Thomas M
TM
D000595:Amino Acid Sequence; D000818:Animals; D001200:Ascaris / Q000378:metabolism / Q000502:physiology*; D003599:Cytoskeleton / Q000378:metabolism / Q000502:physiology*; D015801:Helminth Proteins / Q000378:metabolism / Q000502:physiology*; D007422:Intestines / Q000382:microbiology; D008124:Locomotion / Q000502:physiology; D008297:Male; D008969:Molecular Sequence Data; D011554:Pseudopodia / Q000378:metabolism / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D013081:Sperm Motility / Q000502:physiology*; D013094:Spermatozoa / Q000378:metabolism / Q000502:physiology*
D015801:Helminth Proteins