title: Properties of the C-terminal tail of human mitochondrial inner membrane protein Oxa1L and its interactions with mammalian mitochondrial ribosomes.
abstract: In humans the mitochondrial inner membrane protein Oxa1L is involved in the biogenesis of membrane proteins and facilitates the insertion of both mitochondrial- and nuclear-encoded proteins from the mitochondrial matrix into the inner membrane. The C-terminal approximately 100-amino acid tail of Oxa1L (Oxa1L-CTT) binds to mitochondrial ribosomes and plays a role in the co-translational insertion of mitochondria-synthesized proteins into the inner membrane. Contrary to suggestions made for yeast Oxa1p, our results indicate that the C-terminal tail of human Oxa1L does not form a coiled-coil helical structure in solution. The Oxa1L-CTT exists primarily as a monomer in solution but forms dimers and tetramers at high salt concentrations. The binding of Oxa1L-CTT to mitochondrial ribosomes is an enthalpy-driven process with a K(d) of 0.3-0.8 microM and a stoichiometry of 2. Oxa1L-CTT cross-links to mammalian mitochondrial homologs of the bacterial ribosomal proteins L13, L20, and L28 and to mammalian mitochondrial specific ribosomal proteins MRPL48, MRPL49, and MRPL51. Oxa1L-CTT does not cross-link to proteins decorating the conventional exit tunnel of the bacterial large ribosomal subunit (L22, L23, L24, and L29).
authors.affiliation: Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA.
authors.forename: Md Emdadul
authors.initials: ME
authors.lastname: Haque
authors.forename: Kevin B
authors.initials: KB
authors.lastname: Elmore
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Tripathy
authors.forename: Hasan
authors.initials: H
authors.lastname: Koc
authors.forename: Emine C
authors.initials: EC
authors.lastname: Koc
authors.forename: Linda L
authors.initials: LL
authors.lastname: Spremulli
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D054658:Ribosome Subunits, Large / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; C090858:OXA1 protein; D003576:Electron Transport Complex IV