Structure of the Sgt2/Get5 complex provides insights into GET-mediated targeting of tail-anchored membrane proteins

Aline C. Simon, Peter J. Simpson, Rachael M. Goldstone, Ewelina M. Krysztofinska, James W. Murray, Stephen High, Rivka L. Isaacson

Research output: Contribution to journalArticlepeer-review

Abstract

Small, glutamine-rich, tetratricopeptide repeat protein 2 (Sgt2) is the first known port of call for many newly synthesized tailanchored (TA) proteins released from the ribosome and destined for the GET (Guided Entry of TA proteins) pathway. This leads them to the residential membrane of the endoplasmic reticulum via an alternative to the cotranslational, signal recognition particle-dependent mechanism that their topology denies them. In yeast, the first stage of the GET pathway involves Sgt2 passing TA proteins on to the Get4/Get5 complex through a direct interaction between the N-terminal (NT) domain of Sgt2 and the ubiquitin-like (UBL) domain of Get5. Herewecharacterize this interaction at a molecular level by solving both a solution structure of Sgt2-NT, which adopts a unique helical fold, and a crystal structure of the Get5-UBL. Furthermore, using reciprocal chemical shift perturbation data and experimental restraints, we solve a structure of the Sgt2-NT/Get5-UBL complex, validate it via site-directed mutagenesis, and empirically determine its stoichiometry using relaxation experiments and isothermal titration calorimetry. Taken together, these data provide detailed structural information about the interaction between two key players in the coordinated delivery of TA protein substrates into the GET pathway.
Original languageEnglish
Pages (from-to)1327-1332
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume110
Issue number4
DOIs
Publication statusPublished - 22 Jan 2013

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