Beckmann R P, Mizzen L E, Welch W J
Department of Medicine, University of California, San Francisco 94143.
Science. 1990 May 18;248(4957):850-4. doi: 10.1126/science.2188360.
The 70-kilodalton family of heat shock proteins (Hsp 70) has been implicated in posttranslational protein assembly and translocation. Binding of cytosolic forms of Hsp 70 (Hsp 72,73) with nascent proteins in the normal cell was investigated and found to be transient and adenosine triphosphate (ATP)-dependent. Interaction of Hsp 72,73 with newly synthesized proteins appeared to occur cotranslationally, because nascent polypeptides released prematurely from polysomes in vivo can be isolated in a complex with Hsp 72,73. Moreover, isolation of polysomes from short-term [35S]Met-labeled cells (pulsed) revealed that Hsp 72,73 associated with nascent polypeptide chains. In cells experiencing stress, newly synthesized proteins coimmunoprecipitated with Hsp 72,73; however, in contrast to normal cells, interaction with Hsp 72,73 was not transient. A model consistent with these data suggests that under normal growth conditions, cytosolic Hsp 72,73 interact transiently with nascent polypeptides to facilitate proper folding, and that metabolic stress interferes with these events.
热休克蛋白70（Hsp 70）家族的70千道尔顿蛋白与翻译后蛋白质组装及转运有关。研究了正常细胞中胞质形式的Hsp 70（Hsp 72、73）与新生蛋白质的结合情况，发现这种结合是短暂的且依赖三磷酸腺苷（ATP）。Hsp 72、73与新合成蛋白质的相互作用似乎是在共翻译过程中发生的，因为体内从多核糖体过早释放的新生多肽可与Hsp 72、73形成复合物而被分离出来。此外，从短期[35S]甲硫氨酸标记的细胞（脉冲标记）中分离多核糖体显示，Hsp 72、73与新生多肽链相关。在遭受应激的细胞中，新合成的蛋白质与Hsp 72、73发生共免疫沉淀；然而，与正常细胞不同的是，与Hsp 72、73的相互作用并非短暂的。与这些数据相符的一个模型表明，在正常生长条件下，胞质Hsp 72、73与新生多肽短暂相互作用以促进正确折叠，而代谢应激会干扰这些事件。
