title: Structures of human mitofusin 1 provide insight into mitochondrial tethering.
abstract: Mitochondria undergo fusion and fission. The merging of outer mitochondrial membranes requires mitofusin (MFN), a dynamin-like GTPase. How exactly MFN mediates membrane fusion is poorly understood. Here, we determined crystal structures of a minimal GTPase domain (MGD) of human MFN1, including the predicted GTPase and the distal part of the C-terminal tail (CT). The structures revealed that a helix bundle (HB) formed by three helices extending from the GTPase and one extending from the CT closely attaches to the GTPase domain, resembling the configuration of bacterial dynamin-like protein. We show that the nucleotide-binding pocket is shallow and narrow, rendering weak hydrolysis and less dependence on magnesium ion, and that association of HB affects GTPase activity. MFN1 forms a dimer when GTP or GDP/BeF3-, but not GDP or other analogs, is added. In addition, clustering of vesicles containing membrane-anchored MGD requires continuous GTP hydrolysis. These results suggest that MFN tethers apposing membranes, likely through nucleotide-dependent dimerization.
authors.affiliation: Department of Genetics and Cell Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.|Tianjin Key Laboratory of Protein Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Yuanbo
authors.identifier: http://orcid.org/0000-0002-6589-3677
authors.initials: Y
authors.lastname: Qi
authors.affiliation: School of Medicine, Tsinghua University, Beijing 100084, China.
authors.forename: Liming
authors.initials: L
authors.lastname: Yan
authors.affiliation: School of Medicine, Tsinghua University, Beijing 100084, China.
authors.forename: Caiting
authors.initials: C
authors.lastname: Yu
authors.affiliation: Department of Genetics and Cell Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.|Tianjin Key Laboratory of Protein Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Xiangyang
authors.identifier: http://orcid.org/0000-0002-8463-2755
authors.initials: X
authors.lastname: Guo
authors.affiliation: Department of Genetics and Cell Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.|Tianjin Key Laboratory of Protein Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Genetics and Cell Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.|Tianjin Key Laboratory of Protein Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Hu
authors.affiliation: Department of Genetics and Cell Biology, College of Life Sciences, Nankai University, Tianjin 300071, China.|Tianjin Key Laboratory of Protein Sciences, Nankai University, Tianjin 300071, China.
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Huang
authors.affiliation: School of Medicine, Tsinghua University, Beijing 100084, China huj@ibp.ac.cn louzy@mail.tsinghua.edu.cn raozh@xtal.tsinghua.edu.cn.|National Laboratory of Macromolecules, Institute of Biophysics, Chinese Academy of Science, Beijing 100101, China.
authors.forename: Zihe
authors.initials: Z
authors.lastname: Rao
authors.affiliation: School of Medicine, Tsinghua University, Beijing 100084, China huj@ibp.ac.cn louzy@mail.tsinghua.edu.cn raozh@xtal.tsinghua.edu.cn.
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Lou
authors.affiliation: National Laboratory of Macromolecules, Institute of Biophysics, Chinese Academy of Science, Beijing 100101, China huj@ibp.ac.cn louzy@mail.tsinghua.edu.cn raozh@xtal.tsinghua.edu.cn.
authors.forename: Junjie
authors.identifier: http://orcid.org/0000-0003-4712-2243
authors.initials: J
authors.lastname: Hu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D018360:Crystallography, X-Ray; D020558:GTP Phosphohydrolases / Q000737:chemistry* / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D000072417:Protein Domains; D017433:Protein Structure, Secondary
chemical_list: D033681:Mitochondrial Membrane Transport Proteins; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases; C470017:Mfn1 protein, human