MS11-P03 Structure and function of proteins involved in targeting of tail-anchored membrane proteins to the membrane of ER or chloroplast Chwan-Deng Hsiao (Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan) Tai-Wen Lin (Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan) Hsin-Yang Chang (Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan)email: hsiao@gate.sinica.edu.twNearly 5% of membrane proteins are guided to nuclear, endoplasmic reticulum, mitochondrial, Golgi, or peroxisome membranes by their C-terminal transmembrane domain and are classified as tail-anchored (TA) membrane proteins. During the biosynthesis of TA membrane proteins, their single C-terminal trans-membrane segment is inserted into the ER membrane for orientating the functional domain(s) towards the cytosolic side of the cell. The machinery responsible for this post-translational process has only recently come to light. In yeast, the proteins participating in TA protein insertion was previously identified to be conducted by the GET pathway (Guided Entry of Tail-anchored proteins) including Get1, Get2, Get3, Get4, Get5, Sgt2 and Ybr137wp. In my laboratory, we investigated the interactions between these components from Saccharomyces cerevisiae. Recently, we also determined the crystal structure of arsenite transporter 1 (ArsA1, the homologs of yeast ATPase Get3) from green alga. Our binding activity assay demonstrated that ArsA1 can specifically recognize the transmembrane region of chloroplast TA protein Toc34 but not ER TA protein Sec61β. Based on the ArsA1 structure, we uncover a distinct mechanism for specific filtering between ER and chloroplast TA proteins and successfully manipulate the specificity of mutant ArsA1 for a set of ER TA protein. Our biochemical and structural data provide new insight for the specific selection of ER and chloroplast TA proteins for membrane insertion.References:

Keywords: tail-anchored membrane protein, mitochondrial, chloroplast