POLYSACCHARIDE-PROTEIN COMPLEXES 225 



Operation of Wall Components in Cellular Division 



The mechanism of celhilar division in yeasts has been a subject 

 of investigation in this laboiatorv for many vears. It is intended at 

 this time merelv to indicate briefly the alterations in wall compo- 

 nents that occur during the process of budding. From studies on 

 divisionless mutant strains of Candida albicans it was found ( Nick- 

 erson and Falcone, 1956) that an enzyme (termed "protein disulfide 

 reductase," PDS reductase) which exists in normal strains causes 

 reduction of disulfide bonds of the protein of glucomannan-protein. 

 In the initial stages of this study, the primary glucomannan-protein 

 was employed as substrate. (In an unfortunate typographical con- 

 fusion, the primary glucomannan-protein, when used as substrate 

 for PDS reductase, was referred to as GMP-I in one of our publi- 

 cations, Nickerson and Falcone, 1959. ) In light of our recent frac- 

 tionation of primary GMP, it is hoped that we will be able to identify 

 more precisely the sulfur-rich substrate of PDS reductase. 



The consequences of reduction of disulfide bonds in a wall com- 

 ponent have been interpreted in terms of randomly disordered, 

 covalent-bonded polymer matrices in which localized structural 

 weakness is introduced by rupture of covalent bonds. At the weak- 

 ened site, an explosive blowout occurs, for which evidence has been 

 presented from short-interval, time-lapse photomicrographv ( Nick- 

 erson and Falcone, 1959). The naked protoplasmic sphere that is 

 blown out of the mother cell constitutes the bud-initial. It rapidly 

 becomes covered with wall substance bv growth of the wall sub- 

 stance from the mother cell at the base of the bud-initial. 



The force of the outward thrust at the instant of explosive bud- 

 ding serves to orient the fibrils of the glucan-protein and the spher- 

 ical structures of GMP-I components, as shown in Figs. 6, 9, and 10 

 and discussed in detail elsewhere (Falcone and Nickerson, 1959). 

 The breaking of covalent disulfide bonds within or between compo- 

 nents of the wall fabric sets in motion the train of events witnessed 

 in the budding process: the weakened wall cannot contain the in- 

 ternal pressure, a bud is extruded, and the macromolecular com- 

 ponents, momentarily partially freed of bonding to neighboring 

 components, are ordered by the outward fluid flow into the toroidal 

 pattern that would be predicted from purely physical considerations. 



