分类： 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间： 2016-05-12
Bai, Cuicui
Guo, Peng
Zhao, Qian
Lv, Zongyang
Zhang, Shijia
Gao, Fei
Tian, Zhixi
Liu, Cuimin
Gao, Liyan
Wang, Yingchun
Bai, Cuicui
Guo, Peng
Zhao, Qian
Zhang, Shijia
Wang, Jifeng
Yang, Fuquan
Wang, Jifeng
Yang, Fuquan
摘要： The individual roles of three chloroplast CPN60 protomers (CPN60 alpha, CPN60 beta 1, and CPN60 beta 2) and whether and how they are assembled into functional chaperonin complexes are investigated in Chlamydomonas reinhardtii. Protein complexes containing all three potential subunits were identified in Chlamydomonas, and their co-expression in Escherichia coli yielded a homogeneous population of oligomers containing all three subunits (CPN60 alpha beta 1 beta 2), with a molecular weight consistent with a tetradecameric structure. While homo-oligomers of CPN60 beta could form, they were dramatically reduced when CPN60 alpha was present and homo-oligomers of CPN60 beta 2 were readily changed into hetero-oligomers in the presence of ATP and other protomers. ATP hydrolysis caused CPN60 oligomers to disassemble and drove the purified protomers to reconstitute oligomers in vitro, suggesting that the dynamic nature of CPN60 oligomers is dependent on ATP. Only hetero-oligomeric CPN60 alpha beta 1 beta 2, containing CPN60 alpha, CPN60 beta 1, and CPN60 beta 2 subunits in a 5: 6: 3 ratio, cooperated functionally with GroES. The combination of CPN60 alpha and CPN60 beta subunits, but not the individual subunits alone, complemented GroEL function in E. coli with subunit recognition specificity. Down-regulation of the CPN60 alpha subunit in Chlamydomonas resulted in a slow growth defect and an inability to grow autotrophically, indicating the essential role of CPN60 alpha in vivo.
分类： 生物学 >> 生物物理学 >> 细胞生物学 提交时间： 2016-05-11
Yan, Liming
Wang, Wei
Rao, Zihe
Lou, Zhiyong
Sun, Sha
Shi, Juanming
Hu, Xiaoyu
Hu, Junjie
Sun, Sha
Shi, Juanming
Hu, Xiaoyu
Hu, Junjie
Rao, Zihe
Hu, Junjie
Wang, Wei
Wang, Shiyan
Su, Dan
Su, Dan
Rao, Zihe
Lou, Zhiyong
摘要： Homotypic membrane fusion of the endoplasmic reticulum is mediated by dynamin-like guanosine triphosphatases (GTPases), which include atlastin (ATL) in metazoans and Sey1p in yeast. In this paper, we determined the crystal structures of the cytosolic domain of Sey1p derived from Candida albicans. The structures reveal a stalk-like, helical bundle domain following the GTPase, which represents a previously unidentified configuration of the dynamin superfamily. This domain is significantly longer than that of ATL and critical for fusion. Sey1p forms a side-by-side dimer in complex with GMP-PNP or GDP/AlF4- but is monomeric with GDP. Surprisingly, Sey1p could mediate fusion without GTP hydrolysis, even though fusion was much more efficient with GTP. Sey1p was able to replace ATL in mammalian cells, and the punctate localization of Sey1p was dependent on its GTPase activity. Despite the common function of fusogenic GTPases, our results reveal unique features of Sey1p.
分类： 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间： 2016-05-12
Yu, Zhongsheng
Liu, Jiyong
Jiao, Renjie
Yu, Zhongsheng
Jiao, Renjie
Liu, Jiyong
Jiao, Renjie
Deng, Wu-Min
摘要： More and more studies have shown chromatin remodelers and histone modifiers play essential roles in regulating developmental patterns by organizing specific chromosomal architecture to establish programmed transcriptional profiles, with implications that histone chaperones execute a coordinating role in these processes. Chromatin assembly factor-1 (CAF-1), an evolutionarily conserved three-subunit protein complex, was identified as a histone chaperone coupled with DNA replication and repair in cultured mammalian cells and yeasts. Interestingly, recent findings indicate CAF-1 may have important regulatory roles during development by interacting with specific transcription factors and epigenetic regulators. In this review, we focus on the essential roles of CAF-1 in regulating heterochromatin organization, asymmetric cell division, and specific signal transduction through epigenetic modulations of the chromatin. In the end, we aim at providing a current image of facets of CAF-1 as a histone chaperone to orchestrate cell proliferation and differentiation during multi-cellular organism development.
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