Shires T K, McLaughlin C M, Pitot H C
Biochem J. 1975 Mar;146(3):513-26. doi: 10.1042/bj1460513a.
Differences in the binding sites for polyribosomes, template-depleted ribosomes and large ribosomal subunits were found in microsomal derivatives of the rough endoplasmic reticulum. 1. The stoicheiometry of polyribosome and ribosome interaction in vitro with membranes was shown to be influenced by the relative concentration of interactants and the duration of their mixing. Large ribosomal subunits required a more prolonged mixing schedule to achieve saturation of membranes than did polyribosomes. 2. By using a procedure which minimized the effects on binidng by the stoicheiometric variables, competition between populations of polyribosomes, ribosomes and subunits for membrane sites showed that subunits, and to a lesser extent ribosomes, failed to block polyribosome attachment. 3. Polyribosomes isolated from liver, kidney and hepatoma 5123C entirely bound to a common membrane site, but some polyribosomes from myeloma MOPC-21 bound to other sites, perhaps influenced by their unique nascent proteins. 4. Subunit-binding sites appear on rough membranes only after endogenous polyribosomes have been removed, but no evidence that resulting changes in surface constituents are responsible was found. Large-subunit binding was largely abolished by lowering MgC12 concentration of 0.1 mM, whereas under the same conditions polyribosome binding was undiminished. 5. The large-subunit site appears to be distinct from the polyribosome site not only in the restriction of its affinity for particles but also spatially, to the extent that bound subunits do not hinder access of polyribosomes to their sites.
在糙面内质网的微粒体衍生物中发现了多核糖体、模板耗尽核糖体和大核糖体亚基结合位点的差异。1. 体外多核糖体和核糖体与膜相互作用的化学计量学表明，受相互作用物的相对浓度及其混合持续时间的影响。与多核糖体相比，大核糖体亚基需要更长的混合时间才能使膜达到饱和。2. 通过使用一种将化学计量变量对结合的影响降至最低的方法，多核糖体、核糖体和亚基群体对膜位点的竞争表明，亚基以及程度较轻的核糖体未能阻止多核糖体的附着。3. 从肝脏、肾脏和肝癌5123C分离的多核糖体完全结合到一个共同的膜位点，但骨髓瘤MOPC - 21的一些多核糖体结合到其他位点，这可能受其独特的新生蛋白质影响。4. 只有在内源多核糖体被去除后，亚基结合位点才会出现在糙面膜上，但未发现表面成分的由此产生的变化是其原因的证据。将MgC12浓度降至0.1 mM时，大亚基结合基本被消除，而在相同条件下多核糖体结合不受影响。5. 大亚基位点似乎不仅在对颗粒的亲和力限制方面，而且在空间上与多核糖体位点不同，因为结合的亚基不会阻碍多核糖体进入其位点。
