title: Dissecting stop transfer versus conservative sorting pathways for mitochondrial inner membrane proteins in vivo.
abstract: Mitochondrial inner membrane proteins that carry an N-terminal presequence are sorted by one of two pathways: stop transfer or conservative sorting. However, the sorting pathway is known for only a small number of proteins, in part due to the lack of robust experimental tools with which to study. Here we present an approach that facilitates determination of inner membrane protein sorting pathways in vivo by fusing a mitochondrial inner membrane protein to the C-terminal part of Mgm1p containing the rhomboid cleavage region. We validated the Mgm1 fusion approach using a set of proteins for which the sorting pathway is known, and determined sorting pathways of inner membrane proteins for which the sorting mode was previously uncharacterized. For Sdh4p, a multispanning membrane protein, our results suggest that both conservative sorting and stop transfer mechanisms are required for insertion. Furthermore, the sorting process of Mgm1 fusion proteins was analyzed under different growth conditions and yeast mutant strains that were defective in the import motor or the m-AAA protease function. Our results show that the sorting of mitochondrial proteins carrying moderately hydrophobic transmembrane segments is sensitive to cellular conditions, implying that mitochondrial import and membrane sorting in the physiological environment may be dynamically tuned.
authors.affiliation: School of Biological Sciences, Seoul National University, Building 504-421, Seoul 151-747, South Korea.
authors.forename: Kwangjin
authors.initials: K
authors.lastname: Park
authors.forename: Salomé Calado
authors.initials: SC
authors.lastname: Botelho
authors.forename: Joonki
authors.initials: J
authors.lastname: Hong
authors.forename: Marie
authors.initials: M
authors.lastname: Österberg
authors.forename: Hyun
authors.initials: H
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D060833:Cellular Microenvironment; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D021381:Protein Transport; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C082883:MGM1 protein, S cerevisiae; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D019204:GTP-Binding Proteins