ACYL-BINDING LIPID-TRANSFER PROTEINS FROM RAPE SEEDLINGS, A NOVEL CATEGORY OF PROTEINS INTERACTING WITH LIPIDS

From rape (Brassica napus) seedlings proteins able to bind fatty acids and their CoA-esters were purified by gel filtration and cation-excha nge chromatography. Among the four proteins detected, one of them (pea k IV) appeared purified to homogeneity. This protein is a monomer with a molecular mass of about 9 kDa, as estimated by gel filtration and b y polyacrylamide gel electrophoresis. The isoelectric point of the rap e protein was higher than 10.5 as determined by chromatofocusing. The pure rape protein appeared furthermore to be able to transfer several phospholipids (phosphatidylcholine, phosphatidylinositol and phosphati dylethanolamine) between membranes. The rape protein, having a multifu nctional property, was thus called acyl-binding/lipid-transfer protein (AB-LTP). In order to compare this protein to plant lipid-transfer pr oteins (LTPs), its structure was determined. The amino acid analysis o f the rape AB-LTP revealed a high amount of alanine, an absence of his tidine and tryptophan and the presence of eight cysteine residues. The N-terminal amino acid sequence of the rape protein revealed a high ho mology to plant LTPs. These observations led us to propose that the ra pe AB-LTPs belong to a category of plant proteins interacting with lip ids and playing a role in the fatty acid dynamics.