title: Distinct targeting pathways for the membrane insertion of tail-anchored (TA) proteins.
abstract: Tail-anchored (TA) proteins are characterised by a C-terminal transmembrane region that mediates post-translational insertion into the membrane of the endoplasmic reticulum (ER). We have investigated the requirements for membrane insertion of three TA proteins, RAMP4, Sec61beta and cytocrome b5. We show here that newly synthesised RAMP4 and Sec61beta can accumulate in a cytosolic, soluble complex with the ATPase Asna1 before insertion into ER-derived membranes. Membrane insertion of these TA proteins is stimulated by ATP, sensitive to redox conditions and blocked by alkylation of SH groups by N-ethylmaleimide (NEM). By contrast, membrane insertion of cytochrome b5 is not found to be mediated by Asna1, not stimulated by ATP and not affected by NEM or an oxidative environment. The Asna1-mediated pathway of membrane insertion of RAMP4 and Sec61beta may relate to functions of these proteins in the ER stress response.
authors.affiliation: Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Allianz, Heidelberg, Germany.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Favaloro
authors.forename: Milan
authors.initials: M
authors.lastname: Spasic
authors.forename: Blanche
authors.initials: B
authors.lastname: Schwappach
authors.forename: Bernhard
authors.initials: B
authors.lastname: Dobberstein
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000478:Alkylation; D000818:Animals; D053501:Arsenite Transporting ATPases / Q000378:metabolism*; D015786:Cytochromes b5 / Q000737:chemistry / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006168:Guinea Pigs; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D011817:Rabbits; D000069816:SEC Translocation Channels; D015398:Signal Transduction / Q000502:physiology; D013347:Subcellular Fractions
chemical_list: C489667:GET3 protein, human; D008565:Membrane Proteins; D000069816:SEC Translocation Channels; C499388:SEC61B protein, human; C511174:Serp1 protein, mouse; D000255:Adenosine Triphosphate; D015786:Cytochromes b5; D053501:Arsenite Transporting ATPases