Department of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla, California 92093-0116.
Plant Physiol. 1991 May;96(1):18-25. doi: 10.1104/pp.96.1.18.
A cytosolic pea (Pisum sativum) seed albumin (ALB) and a chimeric protein (PHALB) consisting of the signal peptide and first three amino acids of phytohemagglutinin (PHA) and the amino acid sequence of ALB were expressed in parallel suspension cultures of tobacco (Nicotiana tabacum) cells and their intracellular fates examined. PHALB was efficiently secreted by the cells whereas ALB remained intracellular. These experiments show that the information contained in the signal peptide of a vacuolar protein is both necessary and sufficient for efficient secretion, and define secretion as a default or bulk-flow pathway. Entry into the secretory pathway was accompanied by glycosylation and the efficient conversion of the high mannose glycans into complex glycans indicating that transported glycoproteins do not need specific recognition domains for the modifying enzymes in the Golgi. Tunicamycin depressed the accumulation of the unglycosylated polypeptide in the culture medium much less than the accumulation of other glycoproteins. We interpret this as evidence that glycans on proteins that are not normally glycosylated do not have the same function of stabilizing and protecting the polypeptide as on natural glycoproteins.
在烟草悬浮细胞培养中平行表达了一种胞质豌豆（Pisum sativum）种子白蛋白（ALB）和一种由植物血凝素（PHA）的信号肽和前三个氨基酸以及 ALB 的氨基酸序列组成的嵌合蛋白（PHALB），并检测了它们的细胞内命运。PHALB 被细胞有效地分泌，而 ALB 则留在细胞内。这些实验表明，液泡蛋白信号肽中包含的信息对于有效分泌是必需且充分的，并将分泌定义为默认或批量流途径。进入分泌途径伴随着糖基化和将高甘露糖聚糖高效转化为复杂聚糖，表明转运糖蛋白不需要在高尔基体中用于修饰酶的特异性识别结构域。衣霉素对培养基中未糖基化多肽的积累的抑制作用远小于其他糖蛋白的积累。我们将此解释为证据，表明通常不发生糖基化的蛋白质上的聚糖没有像天然糖蛋白上的聚糖那样具有稳定和保护多肽的相同功能。
