Synthesis of phospholipid transfer proteins from maize seedlings

The synthesis of phospholipid transfer proteins has been studied in vitro after isolation of poly(A)+RNAs from maize seedlings and by in vivo labelling of coleoptiles. After immunoprecipitation of translation products in wheat germ or in reticulocyte lysate systems, the analysis by electrophoresis revealed two bands of molecular mass 9 kDa and 12 kDa. The in vitro synthesized 12 kDa protein is a precursor of the 9 kDa purified protein from maize seedlings as suggested by competition experiments with the pure protein. After immunoprecipitation of in vivo labelled proteins, two bands were detected. One of them, having a molecular mass of 7 kDa, could be related to the in vitro synthesized 9 kDa protein, the other corresponding to the purified protein. Furthermore, biosynthesis of both precursors occurs on membrane-bound polysomes. Presumably a post translational process occurs, yielding to the mature forms.