Structures of Get3, Get4, and Get5 provide new models for TA membrane protein targeting

Abstract

The GET pathway, using several proteins (Gets 1-5 and probably Sgt2), posttranslationally conducts tail-anchored (TA) proteins to the endoplasmic reticulum (ER). At the ER, TA proteins are inserted into the lipid bilayer and then sorted and directed to their respective destinations in the secretory pathway. Until last year, there was no structural information on any of the GET components but now there are ten crystal structures of Get3 in a variety of nucleotide-bound states and conformations. The structures of Get4 and a portion of Get5 also emerged in 2010. This minireview provides a detailed comparison of the GET structures and discusses their mechanistic relevance to TA protein insertion. It also addresses the outstanding gaps in detailed molecular information on this system, including the structures of Get5, Sgt2, and the transmembrane complex comprising Get1 and Get2.