166 MACROMOLECULAR COMPLEXES 



results. One is that the immunochemical behavior of the antiserum 

 to dissolved mitotic apparatus is indistinguishable from that of the 

 antiserum to unfertilized-egg antigens when they are both made to 

 react with solutions of mitotic apparatus. The other is the fusion 

 of the only band assignable to the dissolved mitotic apparatus with 

 one of several assignable to a solution of antigens from unfertilized 

 eggs. The antigen responsible for this band has been termed the 

 precursor-1 component. These results are in complete agreement 

 with the premise that the structural constituents of the mitotic ap- 

 paratus are on hand in the unfertilized egg prior to the onset of the 

 mitotic cycle. On a qualitative basis, at least, there appears to be 

 no need for the egg to synthesize new protein species necessary for 

 the mechanical events of mitosis, once it has left the ovary. The 

 machinery essential for the equipartition of the hereditary material 

 resides unassembled in the unfertilized egg awaiting the signal, 

 brought by the penetration of a sperm, to become aggregated into 

 the definitive mitotic apparatus. 



Another very interesting inference can be drawn from the fusion 

 of the precursor-1 com^ionent band with a band ascribable to an 

 antigen from unfertilized eggs. When the mitotic apparatus was 

 put into solution, it was, in all probability, disassembled by breaking 

 the same links that were formed to assemble the precursor-1 com- 

 ponents into the mitotic apparatus. This is the simplest interpreta- 

 tion for the consistent correlation of the appearance of the precur- 

 sor-1 component with the loss of structural integrity by the mitotic 

 apparatus when the latter is dissolved. It would thus seem that the 

 dissolving of the mitotic apparatus, in terms of the end products 

 observed, may be viewed as the reversal of the assembly process. 

 The very mild conditions under which isolated mitotic apparatus 

 can be dissolved (Mazia, 1959) to vield the precursor-1 component 

 in solution preclude the peptide bond from consideration as the in- 

 termolecular link responsible for the structural integrity of the 

 mitotic apparatus. 



What type of intermolecular cross-links can account for this be- 

 havior? Mazia (1958, 1959) presents evidence, based primarily 

 upon solubility studies of mitotic apparatus isolated by different 

 methods, that intermolecular bridges involving sulfur— thought to be 

 disulfide— are responsible for the polymerization of the molecular 

 subimits into the division figure, although hydrogen-bonding can- 

 not be entirely excluded. The involvement of sulfur-containing 



