Altman R A, Hughey R P
Biochem Int. 1986 Dec;13(6):1009-17.
In order to determine the subcellular site(s) of rat renal gamma-glutamyltranspeptidase propeptide cleavage labeled immunoprecipitates were obtained from preparations of either intracellular membranes or brush border membrane vesicles. Heterodimer accounts for 25% of the label associated with transpeptidase in intracellular membranes from 5 to 40 min postinjection of [35S]methionine, consistent with a cotranslational cleavage of propeptide in the endoplasmic reticulum. Labeled propeptide and heterodimer appear in the brush border membrane fraction between 20-30 min postinjection and accumulate for 1 h and 4h, respectively. Subsequently, the propeptide disappears with a half-life of 1 h while the heterodimer is relatively stable. These results confirm our previous proposal for two distinct subcellular sites for transpeptidase propeptide cleavage (Capraro, M.A. and Hughey, R.P. (1983) FEBS Lett. 157, 139-143).
为了确定大鼠肾脏γ-谷氨酰转肽酶前肽裂解的亚细胞位点，从细胞内膜或刷状缘膜囊泡制剂中获得了标记的免疫沉淀物。在注射[35S]甲硫氨酸后5至40分钟，异二聚体占细胞内膜中转肽酶相关标记的25%，这与内质网中前肽的共翻译裂解一致。标记的前肽和异二聚体在注射后20 - 30分钟出现在刷状缘膜部分，分别积累1小时和4小时。随后，前肽以1小时的半衰期消失，而异二聚体相对稳定。这些结果证实了我们之前提出的转肽酶前肽裂解存在两个不同亚细胞位点的观点（Capraro, M.A.和Hughey, R.P. (1983) FEBS Lett. 157, 139 - 143）。
