Phospholipid transfer protein from maize seedlings is partly membrane-bound

Abstract

Specific antibodies raised against phospholipid transfer protein from maize seeds, react with mitochondria or microsomes solubilized by sodium deoxycholate. A single precipitin line was observed with both types of solubilized membranes when the double immunodiffusion technique was used. When the solubilized membranes were separated by fast-protein liquid chromatography (FPLC) on a reverse phase column, prior to the immunodiffusion, only fractions co-migrating with the pure phospholipid transfer protein, reacted with the antibody. Alternatively, solubilized membranes were submitted to sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), followed by immunoblotting; the detection of antigen-antibody complexes by a peroxydase reagent revealed the presence of a band co-migrating with the pure protein. All these observations strongly suggest that phospholipid transfer proteins are membrane-bound. The physiological significance of this finding will be discussed.