Endophilin and CtBP/BARS are not acyl transferases in endocytosis or Golgi fission

Endophilins have been proposed to have an enzymatic activity ( a lysophosphatidic acid acyl transferase or LPAAT activity) that can make phosphatidic acid in membranes(1-3). This activity is thought to change the bilayer asymmetry in such a way that negative membrane curvature at the neck of a budding vesicle will be stabilized. An LPAAT activity has also been proposed for CtBP/ BARS ( carboxy- terminal binding protein/ brefeldin A- ribosylated substrate), a transcription co- repressor that is implicated in dynamin- independent endocytosis and fission of the Golgi in mitosis(4-6). Here we show that the LPAAT activity associated with endophilin is a contaminant of the purification procedure and can be also found associated with the pleckstrin homology domain of dynamin. Likewise, the LPAAT activity associated with CtBP/ BARS is also a co- purification artefact. The proposed locus of activity in endophilins includes the BAR domain, which has no catalytic site but instead senses positive membrane curvature. These data will prompt a re- evaluation of the molecular details of membrane budding.