Otegui Marisa S, Herder Rachel, Schulze Jan, Jung Rudolf, Staehelin L Andrew
Department of Botany, University of Wisconsin, Madison, Wisconsin 53706, USA.
Plant Cell. 2006 Oct;18(10):2567-81. doi: 10.1105/tpc.106.040931. Epub 2006 Sep 29.
We have investigated the transport of storage proteins, their processing proteases, and the Vacuolar Sorting Receptor-1/Epidermal Growth Factor Receptor-Like Protein1 (VSR-1/ATELP1) receptor during the formation of protein storage vacuoles in Arabidopsis thaliana embryos by means of high-pressure freezing/freeze substitution, electron tomography, immunolabeling techniques, and subcellular fractionation. The storage proteins and their processing proteases are segregated from each other within the Golgi cisternae and packaged into separate vesicles. The storage protein-containing vesicles but not the processing enzyme-containing vesicles carry the VSR-1/ATELP1 receptor. Both types of secretory vesicles appear to fuse into a type of prevacuolar multivesicular body (MVB). We have also determined that the proteolytic processing of the 2S albumins starts in the MVBs. We hypothesize that the compartmentalized processing of storage proteins in the MVBs may allow for the sequential activation of processing proteases as the MVB lumen gradually acidifies.
我们通过高压冷冻/冷冻置换、电子断层扫描、免疫标记技术和亚细胞分级分离,研究了拟南芥胚胎中蛋白质储存液泡形成过程中储存蛋白、其加工蛋白酶以及液泡分选受体-1/表皮生长因子受体样蛋白1(VSR-1/ATELP1)受体的运输情况。储存蛋白及其加工蛋白酶在高尔基潴泡内彼此分离,并被包装到不同的囊泡中。含有储存蛋白的囊泡而非含有加工酶的囊泡携带VSR-1/ATELP1受体。这两种分泌囊泡似乎都融合形成了一种前液泡多囊泡体(MVB)。我们还确定2S白蛋白的蛋白水解加工始于MVBs。我们推测,随着MVB腔逐渐酸化,MVBs中储存蛋白的区室化加工可能允许加工蛋白酶依次激活。