Protocol to determine the topology of integral endoplasmic reticulum membrane protein in Saccharomyces cerevisiae

Here, we present a protocol to determine the topology of Fld1 (few lipid droplets), an integral endoplasmic reticulum (ER) membrane protein in Saccharomyces cerevisiae. We describe steps to generate functional N-terminal GFP and C-terminal mCherry fusion with Fld1. We detail the strategy to perform subcellular fractionation to isolate ER-derived microsomes that were subjected to salt detergent extraction analysis. We then provide procedures to determine the topology of Fld1 using proteinase K treatment.