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Updated: Aug 13, 2026

Determining Membrane Protein Topology Using Fluorescence Protease Protection (FPP)
Published on: April 20, 2015
Identification and evolution of dual-topology membrane proteins
Mikaela Rapp1, Erik Granseth, Susanna Seppälä
1Center for Biomembrane Research, Department of Biochemistry and Biophysics, AlbaNova, Stockholm University, SE-10691 Stockholm, Sweden.
Abstract:
Integral membrane proteins are generally believed to have unique membrane topologies. However, it has been suggested that dual-topology proteins that adopt a mixture of two opposite orientations in the membrane may exist. Here we show that the membrane orientations of five dual-topology candidates identified in Escherichia coli are highly sensitive to changes in the distribution of positively charged residues, that genes in families containing dual-topology candidates occur in genomes either as pairs or as singletons and that gene pairs encode two oppositely oriented proteins whereas singletons encode dual-topology candidates. Our results provide strong support for the existence of dual-topology proteins and shed new light on the evolution of membrane-protein topology and structure.
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