1. MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK

Correspondence to: Harvey T. McMahon¹ Correspondence and requests for materials should be addressed to H.T.McM. (Email: hmm@mrc-lmb.cam.ac.uk).

Abstract

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, 2, 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, 5, 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.

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