Hetero-oligomeric CPN60 resembles highly symmetric group I chaperonin structure revealed by Cryo-EM.
Hetero-oligomeric CPN60 resembles highly symmetric group I chaperonin structure revealed by Cryo-EM.
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异源寡聚 CPN60 类似于冷冻电镜揭示的高度对称的 I 族伴侣蛋白结构。
DOI：
10.1111/tpj.14273
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Cuimin Liu
中科院分区：
文献类型：
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作者：
Qian Zhao;Xiang Zhang;Frederik Sommer;Na Ta;Ning Wang;Michael Schroda;Yao Cong;Cuimin Liu
叶绿体伴侣蛋白系统是光合作用关键酶Rubisco生物合成所必需的。以莱茵衣藻（Chlamydiumreinhardtii）为模型系统，发现其叶绿体伴侣蛋白由CPN 60 α、CPN 60 β1和CPN 60 β2组成，辅伴侣蛋白由CPN 20、CPN 11和CPN 23三个亚基组成。在大肠coli、CPN 20同源寡聚体和所有可能的其他叶绿体共伴侣蛋白异源寡聚体都是功能性的，但在严格胁迫条件下，只有CPN 11/20/23-CPN 60 αβ1β2组成的叶绿体共伴侣蛋白可以完全取代GroES/GroEL。纯化了内源性CPN 60，并确定其化学计量比为CPN 60 α：CPN 60 β1：CPN 60 β2为6：2：6。内源性CPN 60 αβ1β2/ADP和CPN 60 αβ1β2/辅伴侣蛋白/ADP的冷冻电镜结构分别在4.06 nm和3.82 nm处解析。在两种异源寡聚复合物中，每个环内的伴侣蛋白亚基是高度对称的。通过异源寡聚化，叶绿体辅伴侣蛋白CPN 11/20/23形成7个GroES样结构域，其与CPN 60 αβ1β2对称地相互作用。我们的结构还揭示了圆顶形CPN 11/20/23共伴侣蛋白中屋顶形成结构域的不均匀分布，以及CPN 60 αβ1β2伴侣蛋白折叠腔中潜在的多样化表面性质，这可能使叶绿体伴侣蛋白系统能够帮助特定底物的折叠。
The chloroplast chaperonin system is indispensable for the biogenesis of Rubisco, the key enzyme in photosynthesis. Using Chlamydomonas reinhardtii as a model system, we found that in vivo the chloroplast chaperonin consists of CPN60α, CPN60β1, and CPN60β2, and the co-chaperonin of the three subunits CPN20, CPN11 and CPN23. In E. coli, CPN20 homo-oligomers and all possible other chloroplast co-chaperonin hetero-oligomers are functional, but only that consisting of CPN11/20/23-CPN60αβ1β2 can fully replace GroES/GroEL under stringent stress conditions. Endogenous CPN60 was purified and its stoichiometry was determined to be 6:2:6 for CPN60α:CPN60β1:CPN60β2. The cryo-EM structures of endogenous CPN60αβ1β2/ADP and CPN60αβ1β2/co-chaperonin/ADP were solved at resolutions of 4.06 Å and 3.82Å, respectively. In both hetero-oligomeric complexes the chaperonin subunits within each ring are highly symmetric. Through hetero-oligomerization, the chloroplast co-chaperonin CPN11/20/23 forms seven GroES-like domains, which symmetrically interact with CPN60αβ1β2. Our structure also reveals an uneven distribution of roof-forming domains in the dome-shaped CPN11/20/23 co-chaperonin and potentially diversified surface properties in the folding cavity of the CPN60αβ1β2 chaperonin that might enable the chloroplast chaperonin system to assist in the folding of specific substrates.