Anti-chaperone behavior of BiP during the protein disulfide isomerase-catalyzed refolding of reduced denatured lysozyme.
Anti-chaperone behavior of BiP during the protein disulfide isomerase-catalyzed refolding of reduced denatured lysozyme.
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DOI：
10.1016/s0021-9258(18)47329-2
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发表时间：
1994-10
期刊：
影响因子：
--
通讯作者：
A. Puig;H. Gilbert
中科院分区：
文献类型：
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作者：
A. Puig;H. Gilbert
内质网（ER）的折叠催化剂，如蛋白质二硫键异构酶（PDI），加速缓慢的化学步骤，如二硫键形成，伴随蛋白质折叠。ER的分子伴侣，特别是重链结合蛋白BiP（grp 78），以ATP依赖性方式结合和释放未折叠蛋白。在体外，还原的变性溶菌酶的命运取决于底物是否首先与BiP或PDI相互作用。取决于PDI与底物的比率和反应组分混合的顺序，PDI可以表现出折叠酶/伴侣蛋白活性，这增加了溶菌酶重折叠的速率和程度，或者它可以起到促进无活性的二硫键连接的溶菌酶聚集体形成的抗伴侣蛋白的作用（Puig，A.，和吉尔伯特，H.F.（1994）J.Biol.Chem.269，7764-7771）。还原的变性溶菌酶，而不是天然蛋白质，与BiP相互作用，并有效地刺激其肽依赖性ATP酶活性。当以亚化学计量的量存在时，BiP与PDI一样，促进与BiP非共价缔合的大的无活性溶菌酶聚集体的形成。BiP和PDI竞争这些不溶性聚集体中有限数量的位点。如果BiP以高摩尔过量存在，则分子伴侣结合未折叠的溶菌酶，并通过在存在或不存在ATP的情况下将其维持在可溶但无活性的构象来抑制其聚集。增加BiP浓度的程度降低，但不是初始速率，重折叠，这表明BiP和PDI竞争未折叠的溶菌酶和BiP-溶菌酶复合物是不是一个很好的底物PDI无论是在ATP的存在或不存在。根据BiP和PDI的浓度，未折叠的溶菌酶可以在PDI催化的反应中有效地重折叠成天然构象，或者它可以形成可溶性和不溶性BiP-溶菌酶复合物。在体外，PDI和BiP促进的聚集，以及两种蛋白质对底物的竞争，再现了ER质量控制系统的许多特征。
Folding catalysts of the endoplasmic reticulum (ER), such as protein disulfide isomerase (PDI), accelerate the slow chemical steps, such as disulfide bond formation, that accompany protein folding. Molecular chaperones of the ER, notably the heavy chain-binding protein, BiP (grp78), bind and release unfolded proteins in an ATP-dependent fashion. In vitro, the fate of reduced, denatured lysozyme is dependent on whether the substrate interacts first with BiP or PDI. Depending on the ratio of PDI to substrate and order in which the components of the reaction are mixed, PDI can exhibit a foldase/chaperone activity, which increases the rate and extent of lysozyme refolding, or it can function as an anti-chaperone that promotes the formation of inactive, disulfide-linked lysozyme aggregates (Puig, A., and Gilbert, H.F. (1994) J. Biol. Chem. 269, 7764-7771). Reduced, denatured lysozyme, but not the native protein, interacts with BiP and efficiently stimulates its peptide-dependent ATPase activity. When present at substoichiometric amounts, BiP, like PDI, facilitates the formation of large, inactive lysozyme aggregates that are non-covalently associated with BiP. BiP and PDI compete for a limited number of sites in these insoluble aggregates. If BiP is present at a high molar excess, the chaperone binds unfolded lysozyme and inhibits its aggregation by maintaining it in a soluble, yet inactive, conformation, both in the presence or absence of ATP. Increasing concentrations of BiP decrease the extent, but not the initial rate, of refolding, suggesting that BiP and PDI compete for unfolded lysozyme and that the BiP-lysozyme complex is not a very good substrate for PDI either in the presence or absence of ATP. Depending on the BiP and PDI concentrations, unfolded lysozyme may either be efficiently refolded into the native conformation in a PDI-catalyzed reaction, or it may form both soluble and insoluble BiP-lysozyme complexes. In vitro, PDI- and BiP-facilitated aggregation, as well as the competition of the two proteins for substrate, reproduces many of the features of the quality control system of the ER.