BiP and PDI cooperate in the oxidative folding of antibodies in vitro
BiP and PDI cooperate in the oxidative folding of antibodies in vitro
复制标题
DOI：
10.1074/jbc.m002655200
复制
发表时间：
2000-09-22
影响因子：
4.8
通讯作者：
Buchner, J
中科院分区：
文献类型：
--
作者：
Mayer, M;Kies, U;Buchner, J
免疫球蛋白重链结合蛋白(Bip)是Hsp70分子伴侣家族中的一员，它和氧化还原酶蛋白二硫键异构酶(PDI)在内质网蛋白质的折叠和氧化过程中起着重要的作用。然而，目前尚不清楚双方是否在这一进程中进行合作。我们在这里展示了Bip和PDI在变性和还原的Fab片段的体外折叠中的协同作用。通过Rip对未折叠的抗体链进行结合、释放和重新结合的几个依赖于ATP的循环，才能有效地重新激活。我们的数据表明，在没有BiP的情况下，未折叠的抗体链在重折叠时迅速崩溃，使得PDI无法接触到半胱氨酸侧链。BiP结合未折叠的多肽链，并将其保持在半胱氨酸残基可被PDI访问的构象中。这些发现支持了内质网中的折叠辅助蛋白网络的观点，这使得这个细胞器成为一个专门的蛋白质处理室。
Immunoglobulin heavy chain binding protein (BiP), a member of the Hsp70 chaperone family, and the oxidoreductase protein-disulfide isomerase (PDI) play an important role in the folding and oxidation of proteins in the endoplasmic reticulum. However, it was not clear whether both cooperate in this process. We show here that BiP and PDI act synergistically in the in vitro folding of the denatured and reduced Fab fragment. Several ATP-dependent cycles of binding, release, and rebinding of the unfolded antibody chains by Rip are required for efficient reactivation. Our data suggest that in the absence of BiP unfolded antibody chains collapse rapidly upon refolding, rendering cysteine side chains inaccessible for PDI. BiP binds the unfolded polypeptide chains and keeps them in a conformation in which the cysteine residues are accessible for PDI. These findings support the idea of a network of folding helper proteins in the endoplasmic reticulum, which makes this organelle a dedicated protein-processing compartment.