日 時 | 2013年03月27日(水) 16:00 より 17:00 まで |
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講演者 | Dr. Dong-Hua Chen |
講演者所属 | National Center for Macromolecular Imaging, Baylor College of Medicine, Houston TX |
お問い合わせ先 | 村田和義(生理研 形態情報解析室) |
要旨 |
The GroEL/ES chaperonin system is required for the assisted folding of many proteins. How these substrate proteins are encapsulated within the GroEL-GroES cavity is poorly understood. Using symmetry-free, single-particle electron cryo-microscopy, we have characterized a chemically modified mutant of GroEL (EL43Py) that is trapped at a normally transient stage of substrate protein encapsulation. We show that the symmetric pattern of the GroEL subunits is broken as the GroEL cis-ring apical domains reorient to accommodate the simultaneous binding of GroES and a non-native substrate protein (RuBisCO). The collapsed non-native RuBisCO binds to the lower segment of two apical domains, as well as the normally unstructured GroEL C-terminal tails. A comparative structural analysis suggests that the allosteric transitions leading to substrate protein release and folding involve concerted shifts of GroES and the GroEL apical domains and C-terminal tails. |