BIOMOLECULAR ASPECTS OF SPERMATOZOAN MOTILITY 213 



is added. In order to find out if coprecipitates could be formed from 

 alkaline-salt solutions of flagella and muscle protein, extracts from 

 trout sperm flagella were added to trout and rabbit actin (kindly 

 prepared by Dr. G. N. Graham by the methods of Barany et al., 1957) 

 and the ionic strength of the mixture lowered to one-tenth the origi- 

 nal value. Similarly, flagella extracts were added to trout and rabbit 

 myosin (made according to the recommendations of Kessler and 

 Spicer, 1952), and the ionic strength was lowered as before. Myosin, 

 actin, and flagella solutions alone were diluted as controls, and myo- 

 sins and actins were coprecipitated and used to test the activity of the 

 combination. 



The results suggest that the myosin /flagella precipitates were more 

 reactive to ATP than myosin or flagellar protein alone, and the super- 

 natant after precipitation of the myosin/ flagella mixture gave no pre 

 cipitate when acidified to pH 5.0. On the other hand, no precipitate 

 was thrown down by the actin (actin normally lowers the solubility 

 of myosin in salt solutions), and the precipitate from this solution 

 after acidification to pH 5.0 was no more active than the flagellar 

 precipitate alone. Although this does suggest that some combination 

 might have taken place between myosin and flagellar protein to give 

 a synthetic actomyosin of sorts, it is equally possible that coprecipita- 

 tion with myosin has simply improved the mechanical arrangement 

 of the flagellar gel and the myosin has a passive role. 



OTHER EXTRACTION RESULTS 



Failure to extract protein with neutral 0.3M KC1 suggests that 

 little myosin might be present. At the same time, no protein (or at 

 best, only traces of protein) have been extracted from whole flagella 

 and flagella residues by the methods of Barany et al. (1957) for the 

 preparation of actin. 



However, whereas extraction experiments with unicellular algae 

 showed that the cell cytoplasm as well as the flagella contained con- 

 tractile protein, extraction of fish sperm heads resulted in the re- 

 moval of very little (less than 0.1%) material, too small to be ex- 

 amined and certainly within the limits of experimental error. 



After extraction of fish sperm flagella with alkaline salt solutions, 

 examination of the residue in the electron microscope showed that the 

 subfibrils, although disordered and fragmented, seemed to be still 



