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J Biol Chem. 2010 Sep 3;285(36):28353-62. doi: 10.1074/jbc.M110.148262. Epub 2010 Jul 2.

Properties of the C-terminal tail of human mitochondrial inner membrane protein Oxa1L and its interactions with mammalian mitochondrial ribosomes.

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Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA.


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).

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