Chaperonin-assisted folding of glutamine synthetase under nonpermissive conditions: Off-pathway aggregation propensity does not determine the co-chaperonin requirement
Chaperonin-assisted folding of glutamine synthetase under nonpermissive conditions: Off-pathway aggregation propensity does not determine the co-chaperonin requirement
复制标题
DOI：
10.1110/ps.9.12.2405
复制
发表时间：
2000-12-01
期刊：
影响因子：
8
通讯作者：
Fisher, MT
中科院分区：
文献类型：
--
作者：
Voziyan, PA;Fisher, MT
GroEL-GroES空腔的作用之一是提供一个“无限稀释”折叠室，蛋白质底物可以折叠，避免有害的非通路聚集。支持这一假设的一些研究已经得到加强，这些研究表明，在非允许的溶液条件下，即蛋白质不能自发折叠的条件下，强制性的GroES要求。我们发现谷氨酰胺合成酶（GS）的重折叠并不遵循这种模式。在天然渗透物三甲胺n -氧化物（TMAO）或谷氨酸钾存在的情况下，再折叠的GS单体容易聚集成非常大的无活性复合物，即使在低蛋白质浓度下也无法重新激活。令人惊讶的是，在这些“非允许”折叠条件下，GS可以单独与GroEL和ATP一起重新激活，而不需要GroES的封装。相比之下。在另一种低Mg2+不允许条件下，伴侣蛋白依赖性GS的再激活(
One of the proposed roles of the GroEL-GroES cavity is to provide an "infinite dilution" folding chamber where protein substrate can fold avoiding deleterious off-pathway aggregation. Support for this hypothesis has been strengthened by a number of studies that demonstrated a mandatory GroES requirement under nonpermissive solution conditions, i.e., the conditions where proteins cannot spontaneously fold. We have found that the refolding of glutamine synthetase (GS) does not follow this pattern. In the presence of natural osmolytes trimethylamine N-oxide (TMAO) or potassium glutamate, refolding GS monomers readily aggregate into very large inactive complexes and fail to reactivate even at low protein concentration. Surprisingly, under these 'nonpermissive' folding conditions, GS can reactivate with GroEL and ATP alone and does not require the encapsulation by GroES. In contrast. the chaperonin dependent reactivation of GS under another nonpermissive condition of low Mg2+ (