Structural Characterization of the Complex of SecB and Metallothionein-Labeled proOmpA by Cryo-Electron Microscopy |
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| Authors: | Qiang Zhou Shan Sun Phang Tai Sen-Fang Sui |
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| Institution: | 1. State Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China.; 2. Department of Biology, Georgia State University, Atlanta, Georgia, United States of America.; University of South Florida College of Medicine, United States of America, |
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| Abstract: | ProOmpA is a preprotein that is translocated across the plasma membrane by the general secretory pathway in Escherichia coli. The molecular chaperon SecB in Sec pathway can recognize and bind proOmpA for its translocation. However, the structure of the SecB/proOmpA complex remains unknown. Here, we constructed an uncleavable proOmpA fused with metallothionein at its C-terminus and labeled it with metals in vitro for the study of cryo-electron microscopy. Using single particle cryo-electron microscopy, we reconstructed 3D structure of the stable SecB/proOmpA complex. The structure shows that the major portion of preprotein locates on one side of SecB tetramer, resulting in an asymmetric binding pattern. This work also provides a possible approach to the structure determination of small protein complexes by cryo-electron microscopy. |
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