214 FREDERICK G. E. PAUTARD 



present. Even after several days extraction, the 9 pins 2 arrangement 

 could often be detected, and although no information was obtained 

 as to the site from which the contractile protein had been removed, 

 there was also no evidence that obvious structures in the flagellum 

 were involved. 



GENERAL CONCLUSIONS 



The results of experiments on fish sperm tails suggest that a pro- 

 tein which reacts with ATP like a very feeble actomyosin can be 

 extracted from the 9 plus 2 flagella but not from the heads. This pro- 

 tein does not behave characteristically like a myosin since myosin 

 extractants remove no material from the flagellum and there is no 

 x-ray diffraction evidence of the meridional a-reflection at 5.1 A. 

 The changes in the infrared spectrum after acidification suggest that 

 the whole flagellum and its extracts behave more like actin than myo- 

 sin (and the lack of orientation in the x-ray diffraction pattern would 

 seem to support this), but no protein can be removed from the flagel- 

 lum by methods normally used to prepare actin. Although lack of 

 knowledge of special circumstances might have prevented separation 

 of familiar proteins from flagella, it might be that the flagellar protein 

 is not, in fact, an actomyosin but some equally effective complex, pos- 

 sibly in association with lipid. Failure to extract from the sperm heads 

 protein that reacts with ATP seems to be direct evidence that the con- 

 tractile system is confined to the tail. Moreover, the oscillatory be- 

 havior of flagellar gels, apart from the implication that a "flagellum" 

 can be reconstituted as a "model," seems to point to some fundamen- 

 tal mechanism in which the extension and retraction of a filamentous 

 arrangement of molecules may be the property of a complete protein 

 complex. 



SYNERESIS OF ACTIN 



Syneresis of muscle protein is generally regarded as a property of 

 actomyosin and attempts to produce a model contractile system with 

 myosin alone have met with little success. Not only is myosin me- 

 chanically inert to the ATP which it splits, but it also does not seem 

 to react to electrolytes, pH changes, etc., in the way that actomyosin 

 does. Actin "does something" to the myosin (see, for instance, the 



