title: Identification of protein-protein and protein-ribosome interacting regions of the C-terminal tail of human mitochondrial inner membrane protein Oxa1L.
abstract: The mammalian mitochondrial inner membrane protein Oxa1L is involved in the insertion of a number of mitochondrial translation products into the inner membrane. During this process, the C-terminal tail of Oxa1L (Oxa1L-CTT) binds mitochondrial ribosomes and is believed to coordinate the synthesis and membrane insertion of the nascent chains into the membrane. The C-terminal tail of Oxa1L does not contain any Cys residues. Four variants of this protein with a specifically placed Cys residue at position 4, 39, 67, or 94 of Oxa1L-CTT have been prepared. These Cys residues have been derivatized with a fluorescent probe, tetramethylrhodamine-5-maleimide, for biophysical studies. Oxa1L-CTT forms oligomers cooperatively with a binding constant in the submicromolar range. Fluorescence anisotropy and fluorescence lifetime measurements indicate that contacts near a long helix close to position 39 of Oxa1L-CTT occur during oligomer formation. Fluorescence correlation spectroscopy measurements demonstrate that all of the Oxa1L-CTT derivatives bind to mammalian mitochondrial ribosomes. Steady-state fluorescence quenching and fluorescence lifetime data indicate that there are extensive contacts between Oxa1L-CTT and the ribosome-encompassing regions around positions 39, 67, and 94. The results of this study suggest that Oxa1L-CTT undergoes conformational changes and induced oligomer formation when it binds to the ribosome.
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: Linda L
authors.initials: LL
authors.lastname: Spremulli
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Fecko
mesh_terms: D003576:Electron Transport Complex IV / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051336:Mitochondrial Membranes / Q000737:chemistry / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010449:Peptide Mapping / Q000379:methods; D011485:Protein Binding; D055503:Protein Multimerization / Q000502:physiology*; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism*
chemical_list: D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; C090858:OXA1 protein; D003576:Electron Transport Complex IV