Cabib E, Silverman S J, Shaw J A
Laboratory of Biochemistry and Metabolism, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
J Gen Microbiol. 1992 Jan;138(1):97-102. doi: 10.1099/00221287-138-1-97.
Previous results [E. Cabib, A. Sburlati, B. Bowers & S. J. Silverman (1989) Journal of Cell Biology 108, 1665-1672] strongly suggested that the lysis observed in daughter cells of Saccharomyces cerevisiae defective in chitin synthase 1 (Chs1) was caused by a chitinase that partially degrades the chitin septum in the process of cell separation. Consequently, it was proposed that in wild-type cells, Chs1 acts as a repair enzyme by replenishing chitin during cytokinesis. The chitinase requirement for lysis has been confirmed in two different ways: (a) demethylallosamidin, a more powerful chitinase inhibitor than the previously used allosamidin, is also a much better protector against lysis and (b) disruption of the chitinase gene in chs1 cells eliminates lysis. Reintroduction of a normal chitinase gene, by transformation of those cells with a suitable plasmid, restores lysis. The percentage of lysed cells in strains lacking Chs1 was not increased by elevating the chitinase level with high-copy-number plasmids carrying the hydrolase gene. Furthermore, the degree of lysis varied in different chs1 strains; lysis was abolished in chs1 mutants containing the scs1 suppressor. These results indicate that, in addition to chitinase, lysis requires other gene products that may become limiting.
先前的研究结果[E. 卡比布、A. 斯布拉蒂、B. 鲍尔斯和S. J. 西尔弗曼（1989年）《细胞生物学杂志》108卷，1665 - 1672页]有力地表明，在几丁质合成酶1（Chs1）存在缺陷的酿酒酵母子细胞中观察到的裂解现象是由一种几丁质酶引起的，该酶在细胞分离过程中会部分降解几丁质隔膜。因此，有人提出，在野生型细胞中，Chs1在胞质分裂过程中通过补充几丁质起到修复酶的作用。对裂解所需几丁质酶的验证通过两种不同方式得以证实：（a）去甲基别洛沙米定，一种比先前使用的别洛沙米定更强效的几丁质酶抑制剂，也是一种更好的防止细胞裂解的保护剂；（b）chs1细胞中几丁质酶基因的破坏消除了细胞裂解现象。通过用合适的质粒转化这些细胞重新引入正常的几丁质酶基因，可恢复细胞裂解。用携带水解酶基因的高拷贝数质粒提高几丁质酶水平，并不会增加缺乏Chs1的菌株中裂解细胞的百分比。此外，不同的chs1菌株中细胞裂解程度有所不同；含有scs1抑制子的chs1突变体中细胞裂解现象消失。这些结果表明，除了几丁质酶外，细胞裂解还需要其他可能会成为限制因素的基因产物。
