Induction, purification and characterization of acyl carrier protein from developing seeds of oil seed rape ( Brassica napus)

Abstract

The induction kinetics of both acyl carrier protein activity and lipid biosynthesis has been investigated during seed maturation in oil seed rape. Acyl carrier protein is induced prior to the onset of lipid biosynthesis and remains at a high level even after lipid biosynthesis has ceased. Acyl carrier protein was purified from maturing seeds of oil seed rape ( Brassica napus). The protein was found to have limited stability of biological activity, which precluded purification to homogeneity using conventional methods. Purification, to electrophoretic homogeneity, was achieved following specific radiolabelling of the pantotheine domain, of the partially purified protein, with [ 3H]palmitic acid using Escherichia coli acyl ACP synthetase. The acylation introduces both a radiolabel, with which to follow the protein, and a highly hydrophobic domain, which is used as the basis of its further purification. The amino-acid composition of the acyl carrier protein has been determined and is remarkably similar to that reported for the spinach acyl carrier protein. The N-terminal amino-acid sequence of the first 48 residues of rape acyl carrier protein was determined. The sequence shows considerable homology to other plant acyl carrier proteins purified. This report represents the first amino-acid sequence data on a seed acyl carrier protein.