van Engelen F A, Sterk P, Booij H, Cordewener J H, Rook W, van Kammen A, de Vries S C
Department of Molecular Biology, Agricultural University Wageningen, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands.
Plant Physiol. 1991 Jul;96(3):705-12. doi: 10.1104/pp.96.3.705.
EP1, an extracellular protein from carrot (Daucus carota) cell suspensions, has been partially characterized by means of an antiserum and a cDNA clone. In both embryo and suspension cultures different molecular mass EP1 proteins were detected, some of which (31, 32, 52, and 54 kilodaltons) were bound to the cell wall and released into the medium, whereas others (49, 60, and 62 kilodaltons) were more firmly bound to the cell wall and could be extracted with a salt solution. Immunoprecipitation of in vitro translation products revealed a single primary translation product of 45 kilodaltons, suggesting that EP1 heterogeneity is due to differential posttranslational modification. In seedlings organ-specific modification of EP1 proteins was observed, a phenomenon which did not persist in suspension cultures initiated from different seedling organs. In culture EP1 proteins were only found to be associated with vacuolated, nonembryogenic cells, and on these cells they were localized in loosely attached, pectin-containing cell wall material. Purified 52/54 kilodaltons EP1 proteins did not alleviate the inhibitory effect of the glycosylation inhibitor tunicamycin on somatic embryogenesis.
EP1是一种来自胡萝卜（胡萝卜属）细胞悬浮液的细胞外蛋白质，已通过抗血清和cDNA克隆进行了部分表征。在胚胎培养和悬浮培养中均检测到不同分子量的EP1蛋白质，其中一些（31、32、52和54千道尔顿）与细胞壁结合并释放到培养基中，而其他一些（49、60和62千道尔顿）则更牢固地结合在细胞壁上，可用盐溶液提取。体外翻译产物的免疫沉淀显示出一种单一的45千道尔顿初级翻译产物，这表明EP1的异质性是由于翻译后修饰的差异所致。在幼苗中观察到EP1蛋白质的器官特异性修饰，这种现象在由不同幼苗器官起始的悬浮培养中并不持续。在培养物中，仅发现EP1蛋白质与液泡化的非胚性细胞相关，并且在这些细胞上它们定位于松散附着的、含果胶的细胞壁物质中。纯化的52/54千道尔顿EP1蛋白质并未减轻糖基化抑制剂衣霉素对体细胞胚胎发生的抑制作用。
