Holwerda B. C., Galvin N. J., Baranski T. J., Rogers J. C.
Division of Hematology/Oncology, Departments of Internal Medicine and Biology, Washington University School of Medicine, St. Louis, Missouri 63110.
Plant Cell. 1990 Nov;2(11):1091-1106. doi: 10.1105/tpc.2.11.1091.
Aleurain, originally described from its cDNA as a thiol protease [Rogers, J.C., Dean, D., and Heck, G.R. (1985). Proc. Natl. Acad. Sci. USA 82, 6512-6516], is characterized here as a glycoprotein that is targeted to a distinct vacuolar compartment in aleurone cells. Monospecific antibodies to a bacterial trpE-aleurain fusion protein were used to show that aleurain is made as a 42-kilodalton (kD) proenzyme (proaleurain) that is proteolytically processed in a post-Golgi compartment in two steps to form a 32-kD protein. The first processing step is the discrete loss of 9 kD from proaleurain to yield a 33-kD intermediate that is further processed by the gradual loss of 1 kD resulting in mature 32-kD aleurain. Using proaleurain secreted from Xenopus oocytes as a substrate, we established an in vitro system using aleurone cell extracts that correctly processes proaleurain to a stable protein that is indistinguishable from native barley aleurain as judged by partial digestion with staphylococcal V8 protease. Proaleurain is not capable of self-cleavage in the absence of aleurone cell extracts and mature aleurain appears not to participate in processing in vitro.
最初从其cDNA被描述为一种硫醇蛋白酶的糊粉蛋白酶[罗杰斯，J.C.，迪恩，D.，和赫克，G.R.（1985年）。美国国家科学院院刊82，6512 - 6516]，在此被表征为一种糖蛋白，其靶向糊粉层细胞中一个独特的液泡区室。针对细菌trpE - 糊粉蛋白酶融合蛋白的单特异性抗体被用于表明糊粉蛋白酶最初作为一种42千道尔顿（kD）的酶原（前糊粉蛋白酶）产生，该酶原在高尔基体后区室中经过两步蛋白水解加工形成一种32 - kD的蛋白质。第一步加工是前糊粉蛋白酶离散地丢失9 kD以产生一种33 - kD的中间体，该中间体通过逐渐丢失1 kD进一步加工，从而产生成熟的32 - kD糊粉蛋白酶。以非洲爪蟾卵母细胞分泌的前糊粉蛋白酶作为底物，我们使用糊粉层细胞提取物建立了一个体外系统，该系统能将前糊粉蛋白酶正确加工成一种稳定的蛋白质，用葡萄球菌V8蛋白酶部分消化判断，该蛋白质与天然大麦糊粉蛋白酶无法区分。在前糊粉蛋白酶不存在糊粉层细胞提取物的情况下不能自我切割，并且成熟的糊粉蛋白酶似乎不参与体外加工。
