The Kinetic Mechanism of Cation-Catalyzed Phosphatidylglycerol Transbilayer Migration Implies Close Contact between Vesicles as an Intermediate State

Barry R. Lentz, Nancy A. Whitt, Dennis R. Alford*, Stephen W. Burgess, Julie C. Yates, Shlomo Nir

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

We have investigated variations in the rate of Mn2+-catalyzed phosphatidylglycerol transbilayer migration [Lentz, Madden, & Alford (1982) Biochemistry 21, 6799] with changes in phospholipid and cation concentration over more than a 100-fold range of both parameters. The slope of a double logarithmic plot of the rate of transbilayer lipid migration versus lipid concentration was 1.7, suggesting that lipid redistribution was dependent on vesicle aggregation or collision. A model involving transitory dimerization of vesicles was able to account for the concentration dependence of the transbilayer redistribution rate. The observed variation in rate with the logarithm of Mn2+ concentration was complex: linear above 0.4 μM (corresponding to roughly 2.5 Mn2+ per vesicle) but involving a steeper dependence on Mn2+ below 0.04 μM (roughly four vesicles per Mn2+). The rate of transbilayer redistribution increased substantially between 37 and 56 °C, yielding a nonlinear Arrhenius plot. There was no evidence of either fusion or lipid exchange between vesicles at the low concentrations of Mn2+ needed for transbilayer redistribution. The data are consistent with a model suggesting transitory “micro-domains” of a dehydrated, interbilayer complex as involved in the transition state and are inconsistent with a model involving an inverted micelle-type structure for the transition state.

Original languageEnglish
Pages (from-to)4575-4580
Number of pages6
JournalBiochemistry
Volume28
Issue number11
DOIs
StatePublished - 1 May 1989

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