PS transports from the ER membrane to the IM membrane Authored: Williams, MG, 2011-09-14 Edited: Williams, MG, 2011-08-12 Pubmed1898727 Pubmed2332429 Reactome Database ID Release 431483170 Reactome, http://www.reactome.org ReactomeREACT_121037 Transport of phosphatidylserine (PS) occurs via membrane contact sites between the endoplasmic reticulum (ER) membrane and the inner mitochondrial (IM) membrane. This event has been inferred from rats (Vance 1990, Vance 1991).