Patton J L, Srinivasan B, Dickson R C, Lester R L
Department of Biochemistry, College of Medicine, University of Kentucky, Lexington 40536.
J Bacteriol. 1992 Nov;174(22):7180-4. doi: 10.1128/jb.174.22.7180-7184.1992.
To study sphingolipid function(s) in Saccharomyces cerevisiae, we have investigated the effects of environmental stress on mutant (SLC) strains (R. C. Dickson, G. B. Wells, A. Schmidt, and R. L. Lester, Mol. Cell. Biol. 10:2176-2181, 1990) that either contain or lack sphingolipids, depending on whether they are cultured with a sphingolipid long-chain base. Strains lacking sphingolipid were unable to grow at low pH, at 37 degrees C, or with high salt concentrations in the medium; these environmental stresses are known to inhibit the growth of some S. cerevisiae strains with a defective plasma membrane H(+)-ATPase. We found that sphingolipids were essential for proton extrusion at low pH and furthermore found that cells lacking sphingolipid no longer exhibited net proton extrusion at normal pH after a 1-min exposure to pH 3. Cells lacking sphingolipid appeared to rapidly become almost completely permeable to protons at low pH. The deleterious effects of low pH could be partially prevented by 1 M sorbitol in the suspension of cells lacking sphingolipid. Proton extrusion at normal pH (pH 6) was significantly inhibited at 39 degrees C only in cells lacking sphingolipid. Thus, the product of an SLC suppressor gene permits life without sphingolipids only in a limited range of environments. Outside this range, sphingolipids appear to be essential for maintaining proton permeability barriers and/or for proton extrusion.
为了研究酿酒酵母中鞘脂的功能，我们研究了环境胁迫对突变体（SLC）菌株（R.C. 迪克森、G.B. 韦尔斯、A. 施密特和R.L. 莱斯特，《分子细胞生物学》10:2176 - 2181，1990）的影响，这些菌株根据是否与鞘脂长链碱基一起培养而含有或缺乏鞘脂。缺乏鞘脂的菌株在低pH值、37摄氏度或培养基中高盐浓度下无法生长；已知这些环境胁迫会抑制一些质膜H(+) - ATP酶有缺陷的酿酒酵母菌株的生长。我们发现鞘脂对于低pH值下的质子外排至关重要，并且进一步发现缺乏鞘脂的细胞在暴露于pH 3一分钟后，在正常pH值下不再表现出净质子外排。缺乏鞘脂的细胞在低pH值下似乎迅速变得几乎完全对质子通透。在缺乏鞘脂的细胞悬液中，1 M山梨醇可以部分预防低pH值的有害影响。仅在缺乏鞘脂的细胞中，在39摄氏度时正常pH值（pH 6）下的质子外排受到显著抑制。因此，SLC抑制基因的产物仅在有限的环境范围内允许细胞在没有鞘脂的情况下存活。在此范围之外，鞘脂似乎对于维持质子通透屏障和/或质子外排至关重要。
