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Rockefeller University Press, Journal of Cell Biology, 2(179), p. 209-217, 2007

DOI: 10.1083/jcb.200704142

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Novel cargo-binding site in the β and δ subunits of coatomer

Journal article published in 2007 by Kai Michelsen, Volker Schmid, Jutta Metz, Katja Heusser, Urban Liebel, Torsten Schwede ORCID, Anne Spang, Blanche Schwappach, Schmid V Metz J Heusser K Liebel U Schwede T Spang A Schwappach B. Michelsen K.
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Arginine (R)-based ER localization signals are sorting motifs that confer transient ER localization to unassembled subunits of multimeric membrane proteins. The COPI vesicle coat binds R-based signals but the molecular details remain unknown. Here, we use reporter membrane proteins based on the proteolipid Pmp2 fused to GFP and allele swapping of COPI subunits to map the recognition site for R-based signals. We show that two highly conserved stretches--in the beta- and delta-COPI subunits--are required to maintain Pmp2GFP reporters exposing R-based signals in the ER. Combining a deletion of 21 residues in delta-COP together with the mutation of three residues in beta-COP gave rise to a COPI coat that had lost its ability to recognize R-based signals, whilst the recognition of C-terminal di-lysine signals remained unimpaired. A homology model of the COPI trunk domain illustrates the recognition of R-based signals by COPI.