Antebi A, Fink G R
Whitehead Institute of Biomedical Research, Cambridge, Massachusetts.
Mol Biol Cell. 1992 Jun;3(6):633-54. doi: 10.1091/mbc.3.6.633.
PMR1, a Ca(2+)-adenosine triphosphatase (ATPase) homologue in the yeast Saccharomyces cerevisiae localizes to a novel Golgi-like organelle. Consistent with a Golgi localization, the bulk of PMR1 comigrates with Golgi markers in subcellular fractionation experiments, and staining of PMR1 by indirect immunofluorescence reveals a punctate pattern resembling Golgi staining in yeast. However, PMR1 shows only partial colocalization with known Golgi markers, KEX2 and SEC7, in double-label immunofluorescence experiments. The effect of PMR1 on Golgi function is indicated by pleiotropic defects in various Golgi processes in pmr1 mutants, including impaired proteolytic processing of pro-alpha factor and incomplete outer chain glycosylation of invertase. Consistent with the proposed role of PMR1 as a Ca2+ pump, these defects are reversed by the addition of millimolar levels of extracellular Ca2+, suggesting that Ca2+ disposition is essential to normal Golgi function. Absence of PMR1 function partially suppresses the temperature-sensitive growth defects of several sec mutants, and overexpression of PMR1 restricts the growth of others. Some of these interactions are modulated by changes in external Ca2+ concentrations. These results imply a global role for Ca2+ in the proper function of components governing transit and processing through the secretory pathway.
PMR1是酿酒酵母中一种与Ca(2+) - 三磷酸腺苷酶（ATP酶）同源的蛋白，定位于一种新型的类高尔基体细胞器。与高尔基体定位一致，在亚细胞分级分离实验中，大部分PMR1与高尔基体标记物一起迁移，并且通过间接免疫荧光对PMR1进行染色显示出一种点状模式，类似于酵母中的高尔基体染色。然而，在双标记免疫荧光实验中，PMR1仅与已知的高尔基体标记物KEX2和SEC7部分共定位。pmr1突变体中各种高尔基体过程的多效性缺陷表明了PMR1对高尔基体功能的影响，包括前α因子的蛋白水解加工受损和转化酶外链糖基化不完全。与PMR1作为Ca2+泵的推测作用一致，通过添加毫摩尔水平的细胞外Ca2+可以逆转这些缺陷，这表明Ca2+的分布对正常高尔基体功能至关重要。PMR1功能的缺失部分抑制了几个sec突变体的温度敏感生长缺陷，而PMR1的过表达则限制了其他突变体的生长。其中一些相互作用受到外部Ca2+浓度变化的调节。这些结果表明Ca2+在控制分泌途径中转运和加工的组分的正常功能中具有全局作用。
