title: Topological analysis of ATAD3A insertion in purified human mitochondria.
abstract: ATAD3 is a mitochondrial inner membrane-associated protein that has been predicted to be an ATPase but from which no associated function is known. The topology of ATAD3 in mitochondrial membranes is not clear and subject to controversy. A direct interaction of the N-terminal domain (amino-acids 44-247) with the mtDNA has been described, but the same domain has been reported to be sensitive to limited proteolysis in purified mitochondria. Furthermore, ATAD3 has been found in a large purified nucleoid complex but could not be cross-linked to the nucleoid. To resolve these discrepancies we used two immunological approaches to test whether the N-terminal (amino-acids 40-53) and the C-terminal (amino-acids 572-586) regions of ATAD3 are accessible from the cytosol. Using N-terminal and C-terminal specific anti-peptide antibodies, we carried out back-titration ELISA measurements and immuno-fluorescence analysis on freshly purified human mitochondria. Both approaches showed that the N-terminal region of ATAD3A is accessible to antibodies in purified mitochondria. The N-terminal region of ATAD3A is thus probably in the cytoplasm or in an accessible intermembrane space. On the contrary, the C-terminal region is not accessible to the antibody and is probably located within the matrix. These results demonstrate both that the N-terminal part of ATAD3A is outside the inner membrane and that the C-terminal part is inside the matrix.
authors.affiliation: Department of Cell and Developmental Biology, University of Wisconsin, 1988 UCD at Fitzsimons RC-1 South, PO Box 6511, Mail Stop 8108, Aurora, CO 80045, USA.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Hubstenberger
authors.forename: Nicolas
authors.initials: N
authors.lastname: Merle
authors.forename: Romain
authors.initials: R
authors.lastname: Charton
authors.forename: Gérard
authors.initials: G
authors.lastname: Brandolin
authors.forename: Denis
authors.initials: D
authors.lastname: Rousseau
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000235:genetics*; D000595:Amino Acid Sequence; D015153:Blotting, Western; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics*; D008928:Mitochondria / Q000235:genetics*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics*; D008969:Molecular Sequence Data
chemical_list: C549686:ATAD3A protein, human; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D000251:Adenosine Triphosphatases; D000074183:ATPases Associated with Diverse Cellular Activities