Transitional endoplasmic reticulum (tER) consists of confluent rough and smooth endoplasmic reticulum (ER) domains. In a cell-free incubation system, low-density microsomes (1.17 g cc−1) isolated from rat liver homogenates reconstitute tER by Mg2+GTP- and Mg2+ATP-hydrolysis–dependent membrane fusion. The ATPases associated with different cellular activities protein p97 has been identified as the relevant ATPase. The ATP depletion by hexokinase or treatment with either N-ethylmaleimide or anti-p97 prevented assembly of the smooth ER domain of tER. High-salt washing of low-density microsomes inhibited assembly of the smooth ER domain of tER, whereas the readdition of purified p97 with associated p47 promoted reconstitution. The t-SNARE syntaxin 5 was observed within the smooth ER domain of tER, and antisyntaxin 5 abrogated formation of this same membrane compartment. Thus, p97 and syntaxin 5 regulate assembly of the smooth ER domain of tER and hence one of the earliest membrane differentiated components of the secretory pathway.
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机译：过渡性内质网（tER）由汇合的粗糙和光滑内质网（ER）域组成。在无细胞培养系统中，从大鼠肝脏匀浆中分离出的低密度微粒体（1.17 g cc - 1 ）通过Mg 2 + GTP和Mg 2 + ATP水解依赖性膜融合。与不同细胞活性蛋白p97相关的ATPase已被确定为相关的ATPase。通过己糖激酶或用N-乙基马来酰亚胺或抗p97处理的ATP消耗阻止了tER平滑ER域的组装。低盐微粒体的高盐洗涤抑制了tER平滑ER域的组装，而纯化的p97与相关p47的重新组装促进了重组。在tER的平滑ER结构域中观察到了t-SNARE语法蛋白5，而抗共济素5取消了同一膜区室的形成。因此，p97和语法5调节tER平滑ER结构域的组装，从而调节分泌途径中最早的膜分化成分之一。
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