THE TRANSIT SEQUENCE OF A CHLOROPLAST PRECURSOR PROTEIN REORIENTS THELIPIDS IN MONOGALACTOSYL DIGLYCERIDE CONTAINING BILAYERS

The interaction of the chloroplast precursor protein of ferredoxin wit h mixed model membranes composed of H-2 chain labeled monogalactosyl d iacylglycerol and phosphatidylcholine was studied by H-2 and P-31 NMR. The bilayers were found to have special chain packing properties whic h most likely are the result of a specific arrangement of head groups at the interface. The precursor and not the corresponding apoprotein i nduced a bilayer-->isotropic transition in lipid organization as a res ult of the transit sequence-lipid interaction. The implications of the se observations for proteins import into chloroplasts are indicated.