title: Intracellular gene transfer: reduced hydrophobicity facilitates gene transfer for subunit 2 of cytochrome c oxidase.
abstract: Subunit 2 of cytochrome c oxidase (Cox2) in legumes offers a rare opportunity to investigate factors necessary for successful gene transfer of a hydrophobic protein that is usually mitochondrial-encoded. We found that changes in local hydrophobicity were necessary to allow import of this nuclear-encoded protein into mitochondria. All legume species containing both a mitochondrial and nuclear encoded Cox2 displayed a similar pattern, with a large decrease in hydrophobicity evident in the first transmembrane region of the nuclear encoded protein compared with the organelle-encoded protein. Mitochondrial-encoded Cox2 could not be imported into mitochondria under the direction of the mitochondrial targeting sequence that readily supports the import of nuclear encoded Cox2. Removal of the first transmembrane region promotes import ability of the mitochondrial-encoded Cox2. Changing just two amino acids in the first transmembrane region of mitochondrial-encoded Cox2 to the corresponding amino acids in the nuclear encoded Cox2 also promotes import ability, whereas changing the same two amino acids in the nuclear encoded Cox2 to what they are in the mitochondrial-encoded copy prevents import. Therefore, changes in amino acids in the mature protein were necessary and sufficient for gene transfer to allow import under the direction of an appropriate signal to achieve the functional topology of Cox2.
authors.affiliation: Plant Molecular Biology Group, Department of Biochemistry and Molecular Biology, School of Biomedical and Chemical Sciences, University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia.
authors.forename: Daniel O
authors.initials: DO
authors.lastname: Daley
authors.forename: Rachel
authors.initials: R
authors.lastname: Clifton
authors.forename: James
authors.initials: J
authors.lastname: Whelan
mesh_terms: D000595:Amino Acid Sequence; D001692:Biological Transport; D002467:Cell Nucleus / Q000201:enzymology; D003576:Electron Transport Complex IV / Q000235:genetics* / Q000378:metabolism; D007887:Fabaceae / Q000201:enzymology* / Q000235:genetics; D018014:Gene Transfer Techniques; D057927:Hydrophobic and Hydrophilic Interactions; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D013025:Glycine max / Q000201:enzymology* / Q000235:genetics
chemical_list: D003576:Electron Transport Complex IV