Klappa P, Mayinger P, Pipkorn R, Zimmermann M, Zimmermann R
Institut für Physiologische Chemie und Physikalische Biochemie, Universität München, FRG.
EMBO J. 1991 Oct;10(10):2795-803. doi: 10.1002/j.1460-2075.1991.tb07828.x.
Ribonucleoparticle (i.e. ribosome and SRP)-independent transport of proteins into mammalian microsomes is stimulated by a cytosolic ATPase which involves proteins belonging to the hsp70 family. Here we addressed the question of whether there are additional nucleoside triphosphate requirements involved in this transport mechanism. We employed a purified presecretory protein which upon solubilization in dimethyl sulfoxide and subsequent dilution into an aqueous buffer was processed by and transported into mammalian microsomes in the absence of the cytosolic ATPase. Membrane insertion of this precursor protein was found to depend on the hydrolysis of ATP and to involve a microsomal protein which can be photoaffinity inactivated with azido-ATP. Furthermore, a microsomal protein with a similar sensitivity towards photoaffinity modification with azido-ATP was observed to be involved in ribonucleoparticle-dependent transport. We suggest that a novel microsomal protein which depends on ATP hydrolysis is involved in membrane insertion of both ribonucleoparticle-dependent and -independent precursor proteins.
一种涉及hsp70家族蛋白的胞质ATP酶可刺激蛋白质以不依赖核糖核蛋白颗粒（即核糖体和信号识别颗粒）的方式转运到哺乳动物微粒体中。在此，我们探讨了这种转运机制是否还需要其他核苷三磷酸。我们使用了一种纯化的分泌前体蛋白，该蛋白在二甲基亚砜中溶解并随后稀释到水性缓冲液中后，在没有胞质ATP酶的情况下被加工并转运到哺乳动物微粒体中。发现这种前体蛋白的膜插入依赖于ATP的水解，并且涉及一种微粒体蛋白，该蛋白可以被叠氮基ATP光亲和失活。此外，观察到一种对叠氮基ATP光亲和修饰具有相似敏感性的微粒体蛋白参与了依赖核糖核蛋白颗粒的转运。我们认为，一种依赖ATP水解的新型微粒体蛋白参与了依赖和不依赖核糖核蛋白颗粒的前体蛋白的膜插入过程。
