Characterization of the plasma membrane of Mycoplasma laidlawii. III. The formation and aggregation of small lipoprotein structures derived from sodium dodecyl sulfate-solubilized membrane components

Abstract

Small lipoprotein aggregates are formed when sodium dodecyl sulfate-solubilized membrane components are dialyzed against buffer in the absence of divalent cations. These aggregates sediment as a single peak in analytical ultracentrifugation, and their behavior on sucrose density gradient centrifugation indicates that the lipid is bound to the protein. Upon dialysis against buffer containing 0.02 M Mg 2+, the small pieces further aggregate to yield structures having a membrane-like appearance in the electron microscope. The collection of larger aggregates has been designated M r′ (reaggregated membrane prime) and has a buoyant density of 1.18 ± 0.05 g/cm 3 . M r′ is similar to the original membrane in having the same protein to lipid ratio and the same magnesium to protein ratio.