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

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

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).

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cattle
  • Electron Transport Complex IV / chemistry*
  • Electron Transport Complex IV / metabolism*
  • Humans
  • Mitochondria / metabolism*
  • Mitochondrial Proteins / chemistry*
  • Mitochondrial Proteins / metabolism*
  • Models, Molecular
  • Molecular Sequence Data
  • Nuclear Proteins / chemistry*
  • Nuclear Proteins / metabolism*
  • Protein Binding
  • Protein Multimerization
  • Protein Structure, Quaternary
  • Protein Structure, Secondary
  • Ribosome Subunits, Large / metabolism
  • Ribosomes / metabolism*

Substances

  • Mitochondrial Proteins
  • Nuclear Proteins
  • OXA1 protein
  • Electron Transport Complex IV