title: In search of tail-anchored protein machinery in plants: reevaluating the role of arsenite transporters.
abstract: Although the mechanisms underlying selective targeting of tail-anchored (TA) membrane proteins are well established in mammalian and yeast cells, little is known about their role in mediating intracellular membrane trafficking in plant cells. However, a recent study suggested that, in green algae, arsenite transporters located in the cytosol (ArsA1 and ArsA2) control the insertion of TA proteins into the membrane-bound organelles. In the present work, we overproduced and purified these hydrophilic proteins to near homogeneity. The analysis of their catalytic properties clearly demonstrates that C. reinhardtii ArsA proteins exhibit oxyanion-independent ATPase activity, as neither arsenite nor antimonite showed strong effects. Co-expression of ArsA proteins with TA-transmembrane regions showed not only that the former interact with the latter, but that ArsA1 does not share the same ligand specificity as ArsA2. Together with a structural model and molecular dynamics simulations, we propose that C. reinhadtii ArsA proteins are not arsenite transporters, but a TA-protein targeting factor. Further, we propose that ArsA targeting specificity is achieved at the ligand level, with ArsA1 mainly carrying TA-proteins to the chloroplast, while ArsA2 to the endoplasmic reticulum.
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.
authors.forename: Manuel
authors.initials: M
authors.lastname: Maestre-Reyna
authors.affiliation: Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan.
authors.forename: Shu-Mei
authors.initials: SM
authors.lastname: Wu
authors.affiliation: Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan.
authors.forename: Yu-Ching
authors.initials: YC
authors.lastname: Chang
authors.affiliation: Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan.|Doctoral Degree Program in Marine Biotechnology, National Sun Yat-Sen University, 70 Lien-Hai Road, Kaohsiung 80424, Taiwan.|Doctoral Degree Program in Marine Biotechnology, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 11529, Taiwan.
authors.forename: Chi-Chih
authors.initials: CC
authors.lastname: Chen
authors.affiliation: Escuela Tecnica Superior de Ingenierios Industriales, Universidad Politecnica de Valencia, Valencia, Spain.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Maestre-Reyna
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.|Core Facilities for Protein Structural Analysis, Academia Sinica, Taipei, Taiwan.|PhD Program for Translational Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan.
authors.forename: Andrew H-J
authors.initials: AH
authors.lastname: Wang
authors.affiliation: Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan.|Doctoral Degree Program in Marine Biotechnology, National Sun Yat-Sen University, 70 Lien-Hai Road, Kaohsiung 80424, Taiwan.|The Asia-Pacific Ocean Research Center, National Sun Yat-sen University, Kaohsiung 804, Taiwan.
authors.forename: Hsin-Yang
authors.initials: HY
authors.lastname: Chang
mesh_terms: D000595:Amino Acid Sequence; D053501:Arsenite Transporting ATPases / Q000378:metabolism; D018053:Arsenites / Q000378:metabolism*; D002696:Chlamydomonas / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism*; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D018053:Arsenites; D008565:Membrane Proteins; D010940:Plant Proteins; D053501:Arsenite Transporting ATPases