title: Crystal structure and functional analysis of MiD49, a receptor for the mitochondrial fission protein Drp1.
abstract: Mitochondrial fission requires recruitment of dynamin-related protein 1 (Drp1) to the mitochondrial surface, where assembly leads to activation of its GTP-dependent scission function. MiD49 and MiD51 are two receptors on the mitochondrial outer membrane that can recruit Drp1 to facilitate mitochondrial fission. Structural studies indicated that MiD51 has a variant nucleotidyl transferase fold that binds an ADP co-factor essential for activation of Drp1 function. MiD49 shares sequence homology with MiD51 and regulates Drp1 function. However, it is unknown if MiD49 binds an analogous co-factor. Because MiD49 does not readily crystallize, we used structural predictions and biochemical screening to identify a surface entropy reduction mutant that facilitated crystallization. Using molecular replacement, we determined the atomic structure of MiD49 to 2.4 Å. Like MiD51, MiD49 contains a nucleotidyl transferase domain; however, the electron density provides no evidence for a small-molecule ligand. Structural changes in the putative nucleotide-binding pocket make MiD49 incompatible with an extended ligand like ADP, and critical nucleotide-binding residues found in MiD51 are not conserved. MiD49 contains a surface loop that physically interacts with Drp1 and is necessary for Drp1 recruitment to the mitochondrial surface. Our results suggest a structural basis for the differential regulation of MiD51- versus MiD49-mediated fission.
authors.affiliation: Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, 91125.
authors.forename: Oliver C
authors.initials: OC
authors.lastname: Losón
authors.forename: Shuxia
authors.initials: S
authors.lastname: Meng
authors.forename: Huu
authors.initials: H
authors.lastname: Ngo
authors.forename: Raymond
authors.initials: R
authors.lastname: Liu
authors.forename: Jens T
authors.initials: JT
authors.lastname: Kaiser
authors.forename: David C
authors.initials: DC
authors.lastname: Chan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D034281:Dynamins / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D051379:Mice; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010445:Peptide Elongation Factors / Q000737:chemistry* / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: D024101:Mitochondrial Proteins; D010445:Peptide Elongation Factors; C486391:Dnm1l protein, mouse; D034281:Dynamins
keywords: MiD49; dynamin-related protein; mitochondrial dynamics; mitochondrial fission