PPIase domain of trigger factor acts as auxiliary chaperone site to assist the folding of protein substrates bound to the crevice of trigger factor.
PPIase domain of trigger factor acts as auxiliary chaperone site to assist the folding of protein substrates bound to the crevice of trigger factor.
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DOI：
10.1016/j.biocel.2010.01.019
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发表时间：
2010-06
期刊：
影响因子：
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通讯作者：
Chuan-Peng Liu;Qi-Ming Zhou;Dong-Jie Fan;Jun‐mei Zhou
中科院分区：
文献类型：
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作者：
Chuan-Peng Liu;Qi-Ming Zhou;Dong-Jie Fan;Jun‐mei Zhou
触发因子（Trigger Factor，TF）是细菌中新生链遇到的第一个分子伴侣，由肽基脯氨酰顺反异构酶（Peptidyl-prolyl-cis/trans-isomerase，PPIase）结构域和由N-和C-末端结构域构成的缝隙组成。虽然裂缝被认为是提供了一个保护性的空间在核糖体的肽出口位点的新生多肽折叠，目前还不清楚是否PPIase结构域直接参与协助蛋白质折叠。在这里，我们介绍了不同区域的TF的结构变化，并研究其对伴侣功能的TF在协助折叠的各种底物蛋白，包括寡聚甘油醛-3-磷酸脱氢酶（GAPDH）和单体碳酸酐酶II（CA II）和溶菌酶的影响。结果表明，在PPIase活性位点的位点特异性突变或从TF的PPIase结构域的缺失的结构干扰影响TF对CA II和GAPDH的伴侣活性，但没有影响TF辅助溶菌酶的复性，这表明PPIase结构域参与协助折叠的底物大于溶菌酶。突变体的结构干扰的缝隙完全失去了伴侣活性对所有的底物，我们在这项调查中使用。这些结果进一步证实了缝隙是TF的主要伴侣位点，而PPIase结构域中的疏水口袋作为辅助位点以底物依赖的方式协助与缝隙结合的底物蛋白折叠，这有利于TF通过改变保护空间和结合亲和力为蛋白折叠提供适当的帮助。
Trigger factor (TF) is the first chaperone encountered by nascent chains in bacteria, which consists of two modules: peptidyl-prolyl-cis/trans-isomerase (PPIase) domain and a crevice built by both N- and C-terminal domains. While the crevice is suggested to provide a protective space over the peptide exit site of ribosome for nascent polypeptides to fold, it remains unclear whether PPIase domain is directly involved in assisting protein folding. Here, we introduced structural change into different regions of TF, and investigated their influence on the chaperone function of TF in assisting the folding of various substrate proteins, including oligomeric glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and monomeric carbonic anhydrase II (CA II) and lysozyme. Results showed that structural disturbances by site-specific mutations in the PPIase active site or by deletion of the PPIase domain from TF affected the chaperone activity of TF toward CA II and GAPDH but had no effect on TF-assisted lysozyme refolding, suggesting PPIase domain is involved in assisting the folding of substrates larger than lysozyme. Mutants with the structural disturbances in the crevice totally lost the chaperone activity toward all the substrates we used in this investigation. These results provide further evidence to confirm that the crevice is the major chaperone site of TF, and the hydrophobic pocket in PPIase domain acts as an auxiliary site to assist the folding of substrate proteins bound to the crevice in a substrate-dependent manner, which is beneficial for TF to provide appropriate assistance for protein folding by changing protective space and binding affinity.