title: Role of Tim21 in mitochondrial translocation contact sites.
abstract: Translocation of preproteins with N-terminal presequences into mitochondria requires the cooperation of the translocase of the outer membrane (TOM complex) and the presequence translocase of the inner membrane (TIM23 complex). However, the molecular nature of the translocation contact sites is poorly understood. We have identified a novel component of the TIM23 translocase, Tim21, which is involved in their formation. Tim21 is anchored in the mitochondrial inner membrane by a single transmembrane domain and exposes its C-terminal domain into the intermembrane space. The purified C-terminal domain of Tim21 appears not to bind to any of the TIM23 components but rather specifically interacts with the TOM complex. We propose that Tim21 binds to the trans site of the TOM complex thus keeping the two translocases in close contact.
authors.affiliation: Institut für Physiologische Chemie, Universität München, Butenandtstrasse 5, 81377 München, Germany.
authors.forename: Dejana
authors.initials: D
authors.lastname: Mokranjac
authors.forename: Dusan
authors.initials: D
authors.lastname: Popov-Celeketić
authors.forename: Kai
authors.initials: K
authors.lastname: Hell
authors.forename: Walter
authors.initials: W
authors.lastname: Neupert
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D017931:DNA Primers; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D008969:Molecular Sequence Data; D021381:Protein Transport / Q000502:physiology; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; C500397:Tim21 protein, S cerevisiae