236 J- TIBBS 



of a flagellar relaxing factor. Various fractions from the milt of the 

 brown trout (Saimo trutta) were examined to find out what effect, if 

 any, these fractions had on the flagellar ATPase. These results are 

 summarized in Table I. Potassium oxalate (2.5 mM) was normally 

 included in the activity determinations since calcium ions are known 

 to inhibit the muscle relaxing factor (Bozler, 1952). Minimal concen- 

 trations of magnesium activator were employed, and therefore any 

 inhibition arising from magnesium chelation (Perry and Grey, 1956) 

 should have been detectable. The "final supernatant" of the third 

 column was the supernatant obtained from the spermatozoa after 

 these had been homogenized in 0.05Af potassium chloride (which in 

 the case of rabbit muscle would extract the relaxing factor) and the 

 heads and tails removed from this suspension by centrifugation. 



It appears from the results that no one fraction is capable of caus- 

 ing enzyme inhibition.The possibility that a relaxing factor may be 

 firmly attached to the flagellum and may be extracted only with 

 difficulty cannot be ignored. Indeed the high degree of control and 

 the fact that one part of the flagellum may be relaxing while another 

 part is contracting may be urged as indicating the probability of a 

 firm attachment of a factor at significant points. However, as a con- 

 sequence of this, in activity estimations, the sperm tail would show the 

 reduced activity. The measured activity is always entirely adequate 

 to account for the energy required (Tibbs, 1957; Nelson, 1958), and 

 no anomalous results have ever been obtained to suggest that under 

 certain circumstances the enzyme may possess enhanced activity cor- 

 responding to the accidental removal of a relaxing factor. The evi- 

 dence in this case, therefore, indicates the absence of an ATPase in- 

 hibitor in trout milt and of a relaxing factor operating by a process 

 involving enzyme inhibition. 



Whatever the actual mechanism of flagellation, it seems evident 

 that two processes must be involved. In one of these, ATP is split, 

 and the energy liberated is used for motility. In the second process, 

 ATP is not hydrolyzed, but those events taking place on ATP split- 

 ting are reversed, and the component in question returns to its origi- 

 nal condition. In the case of muscle, the cell models of Hoffmann- 

 Berling (1954), and the tail of the bacteriophage T 2 adsorbed on the 

 host (Kozloff and Lute, 1959), the process of ATP splitting- is accom- 

 panied by contraction. This is not a universal rule in systems show- 



