170 PROTEINS OF SEA URCHIN EGG 



crease of the proteins soluble in IM KCl, and he was also able 

 to trace this fraction in the extracts of unfertilized eggs as the 

 one that is precipitated by 50% saturation with ammonium sul- 

 fate. 



Later the present writer and his co-workers undertook a sys- 

 tematic investigation of the changes taking place in the proteins 

 of the egg upon fertilization. The results of these investigations 

 are summarized here. 



Water extracts of sea urchin eggs were submitted to electro- 

 phoretic analysis, and it was shown that a few minutes after 

 fertilization a small new component appears. However, this com- 

 ponent is no longer detectable thirty minutes after fertilization. 

 The extracts were then fractionated with ammonium sulfate, 

 and the fractions were studied electrophoretically. The following 

 facts were established: (a) a decrease in solubility of one com- 

 ponent immediately after fertilization and (b) a splitting of a 

 component present in the unfertilized eggs, thus giving rise to 

 a new component (Monroy, 1950). Further changes of solubility 

 were also shown to take place, but on the whole these were 

 somewhat irregular and hence difficult to interpret ( Monroy and 

 Monroy-Oddo, 1951). 



In the first investigations of Mirsky and in those of the pr-esent 

 writer, lyophilized eggs were used. This introduces the possibility 

 of artifacts. Hence in subsequent work only fresh material has 

 been used, and special precautions have also been taken to avoid 

 secondary alterations during preparation (Giardina and Monroy, 

 1955; Ceas, Impellizzeri, and Monroy, 1955). In the latter in- 

 vestigations attention was focused on a fraction which is precipi- 

 tated by 50% saturation with ammonium sulfate. Three com- 

 ponents are indicated in this fraction by the electrophoretic 

 analysis. Upon treatment with trypsin the fraction prepared from 

 unfertilized eggs is split into live components, whereas the one 

 prepared from fertilized eggs is split into four components (Fig. 

 1) (D'Amelio, 1955). Comparable results were obtained when 

 the action of trypsin on these proteins was followed by chemical 

 determinations (Fig. 2) (Giardina and Monroy, 1955). Proteins 

 from unfertilized and fertilized eggs also behave differently in 



