Transbilayer movement of fluorescent phospholipids in Bacillus megaterium membrane vesicles. Academic Article uri icon

Overview

abstract

  • We investigated the transbilayer movement or flip-flop of phospholipids in vesicles derived from the cytoplasmic membrane of Bacillus megaterium. Since common assay techniques were found to be inapplicable to the Bacillus system, we exploited and elaborated a newly described method in which fluorescent phospholipids (1-myristoyl-2-C6-NBD phospholipids) are used as tracers to monitor flip-flop. These lipids were introduced into Bacillus vesicles from synthetic donor vesicles containing a fluorescence quencher. Transport was measured by monitoring the increase in fluorescence as the tracers departed the quenched environment of the donor vesicle and entered first the outer membrane leaflet and subsequently the inner leaflet of Bacillus vesicles. Independent experiments involving cobalt quenching of NBD fluorescence provided results consistent with the existence of pools of fluorescent phospholipid in the outer and inner leaflets of Bacillus vesicles at the completion of transport. Using the assay we show that phospholipid flip-flop in Bacillus vesicles occurs rapidly (half-time approximately 30 s at 37 degrees C) with no preference for a particular phospholipid headgroup and that it is sensitive to proteolysis. We also establish that flip-flop does not occur in synthetic phospholipid vesicles or vesicles made from Bacillus phospholipids. We conclude that Bacillus vesicles possess the ability to promote rapid transbilayer movement of phospholipids, and that the transport is probably protein (flippase)-mediated.

publication date

  • April 22, 1997

Research

keywords

  • Bacillus megaterium
  • Lipid Bilayers
  • Phospholipid Transfer Proteins
  • Phospholipids

Identity

Scopus Document Identifier

  • 0038147622

Digital Object Identifier (DOI)

  • 10.1021/bi962513h

PubMed ID

  • 9125519

Additional Document Info

volume

  • 36

issue

  • 16