Identification of a targeting factor for posttranslational membrane protein insertion into the ER.
Hundreds of proteins are anchored in intracellular membranes by a single transmembrane domain (TMD) close to the C terminus. Although these tail-anchored (TA) proteins serve numerous essential roles in cells, components of their targeting and insertion pathways have long remained elusive. Here we reveal a cytosolic TMD recognition complex (TRC) that targets TA proteins for insertion into the ER membrane. The highly conserved, 40 kDa ATPase subunit of TRC (which we termed TRC40) was identified as Asna-1. TRC40/Asna-1 interacts posttranslationally with TA proteins in a TMD-dependent manner for delivery to a proteinaceous receptor at the ER membrane. Subsequent release from TRC40/Asna-1 and insertion into the membrane depends on ATP hydrolysis. Consequently, an ATPase-deficient mutant of TRC40/Asna-1 dominantly inhibited TA protein insertion selectively without influencing other translocation pathways. Thus, TRC40/Asna-1 represents an integral component of a posttranslational pathway of membrane protein insertion whose targeting is mediated by TRC.
Stefanovic
Sandra
S
Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Hegde
Ramanujan S
RS
D000595:Amino Acid Sequence; D000818:Animals; D053501:Arsenite Transporting ATPases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007425:Intracellular Membranes / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport; D050765:Qa-SNARE Proteins / Q000378:metabolism; D051381:Rats; D000069816:SEC Translocation Channels; D018271:Signal Recognition Particle / Q000378:metabolism
C489667:GET3 protein, human; D008565:Membrane Proteins; D021122:Protein Subunits; D050765:Qa-SNARE Proteins; D000069816:SEC Translocation Channels; C499388:SEC61B protein, human; D018271:Signal Recognition Particle; D053501:Arsenite Transporting ATPases