title: Dual subcellular distribution of cytochrome b5 in plant, cauliflower, cells.
abstract: Subfractionation studies showed that cytochrome b(5) (cyt b5), which has been considered to be a typical ER protein, was localized in both the endoplasmic reticulum membrane (ER) and the outer membrane of mitochondria in cauliflower (Brassica olracea) cells and was a component of antimycin A-insensitive NADH-cytochrome c reductase system in both membranes. When cDNA for cauliflower cyt b5 was introduced into mammalian (COS-7) and yeast cells as well as into onion cells, the expressed cytochrome was localized both in the ER and mitochondria in those cells. On the other hand, rat and yeast cyt b5s were specifically localized in the ER membranes even in the onion cells. Mutation experiments showed that cauliflower cyt b5 carries information that targets it to the ER and mitochondria within the carboxy-terminal 10 amino acids, as in the case of rat and yeast cyt b5s, and that replacement of basic amino acids in this region of cauliflower cyt b5 with neutral or acidic ones resulted in its distribution only in the ER. Together with the established findings of the importance of basic amino acids in mitochondrial targeting signals, these results suggest that charged amino acids in the carboxy-terminal portion of cyt b5 determine its location in the cell, and that the same mechanism of signal recognition and of protein transport to organelles works in mammalian, plant, and yeast cells.
authors.affiliation: Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka 812-8581. a.itoscc@mbox.nc.kyushu-u.ac.jp
authors.forename: Jingfang
authors.initials: J
authors.lastname: Zhao
authors.forename: Toshimitu
authors.initials: T
authors.lastname: Onduka
authors.forename: Jun-ya
authors.initials: JY
authors.lastname: Kinoshita
authors.forename: Masanori
authors.initials: M
authors.lastname: Honsho
authors.forename: Toshinori
authors.initials: T
authors.lastname: Kinoshita
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Shimazaki
authors.forename: Akio
authors.initials: A
authors.lastname: Ito
mesh_terms: D024361:Amino Acids, Basic / Q000032:analysis; D000818:Animals; D001937:Brassica / Q000737:chemistry* / Q000378:metabolism; D019556:COS Cells; D015786:Cytochromes b5 / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000737:chemistry* / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D008861:Microsomes / Q000737:chemistry; D008928:Mitochondria / Q000737:chemistry* / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000032:analysis; D019697:Onions / Q000737:chemistry; D010944:Plants / Q000737:chemistry*; D021381:Protein Transport; D051381:Rats; D015003:Yeasts / Q000378:metabolism
chemical_list: D024361:Amino Acids, Basic; D015786:Cytochromes b5; D009245:NADH Dehydrogenase