Protein targeting. Structure of the Get3 targeting factor in complex with its membrane protein cargo.
Tail-anchored (TA) proteins are a physiologically important class of membrane proteins targeted to the endoplasmic reticulum by the conserved guided-entry of TA proteins (GET) pathway. During transit, their hydrophobic transmembrane domains (TMDs) are chaperoned by the cytosolic targeting factor Get3, but the molecular nature of the functional Get3-TA protein targeting complex remains unknown. We reconstituted the physiologic assembly pathway for a functional targeting complex and showed that it comprises a TA protein bound to a Get3 homodimer. Crystal structures of Get3 bound to different TA proteins showed an α-helical TMD occupying a hydrophobic groove that spans the Get3 homodimer. Our data elucidate the mechanism of TA protein recognition and shielding by Get3 and suggest general principles of hydrophobic domain chaperoning by cellular targeting factors.
Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
Agnieszka
A
Mateja
Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
Marcin
M
Paduch
Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
Hsin-Yang
HY
Chang
Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
Anna
A
Szydlowska
Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
Anthony A
AA
Kossiakoff
MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK. rhegde@mrc-lmb.cam.ac.uk bkeenan@uchicago.edu.
Ramanujan S
RS
Hegde
Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA. rhegde@mrc-lmb.cam.ac.uk bkeenan@uchicago.edu.
Robert J
RJ
Keenan
D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D003600:Cytosol / Q000201:enzymology; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism
D020662:Guanine Nucleotide Exchange Factors; D008565:Membrane Proteins; D018832:Molecular Chaperones; D046912:Multiprotein Complexes; D029701:Saccharomyces cerevisiae Proteins; D000251:Adenosine Triphosphatases; C529048:Get3 protein, S cerevisiae