Thibodeau S N, Walsh K A
Ann N Y Acad Sci. 1980;343:180-91. doi: 10.1111/j.1749-6632.1980.tb47251.x.
The signal peptidases from both chicken oviduct and dog pancreas microsomes have been detected by a post-translational assay and, in the case of dog microsomes, by a cotranslational assay. This proteolytic activity is not sensitive to a variety of conventional protease inhibitors under the conditions used in these assays. Using a synthetic ester substrate, two additional activities have been observed in oviduct microsomes, but neither appears to correspond to the signal peptidase activity. Using cDNA as a probe for specific mRNAs, it was shown that polysomes, in the process of synthesizing secretory proteins, bind to microsomal membrane vesicles. This binding appears to be dependent on the nature of the translation product (presumably the specific signal peptide) rather than on the mRNA itself. In addition, pretreatment of the membrane vesicles with N-ethyl maleimide prevents the vectorial discharge and processing of several secretory proteins but does not inhibit the binding of their polysomes to membranes.
鸡输卵管和犬胰腺微粒体中的信号肽酶已通过翻译后检测法得以检测，对于犬微粒体而言，还通过共翻译检测法进行了检测。在这些检测所使用的条件下，这种蛋白水解活性对多种传统蛋白酶抑制剂不敏感。使用一种合成酯底物时，在输卵管微粒体中观察到另外两种活性，但似乎都与信号肽酶活性不对应。使用互补脱氧核糖核酸（cDNA）作为特定信使核糖核酸（mRNA）的探针表明，在合成分泌蛋白的过程中，多核糖体与微粒体膜囊泡结合。这种结合似乎取决于翻译产物的性质（大概是特定的信号肽），而不是mRNA本身。此外，用N - 乙基马来酰亚胺对膜囊泡进行预处理可阻止几种分泌蛋白的定向释放和加工，但不抑制它们的多核糖体与膜的结合。
