In vitro conversion of recombinant human proapolipoprotein A-I to apolipoprotein A-I.

We recently investigated the in vivo conversion of recombinant human proapolipoprotein A-I (rh-Met-proapo A-I) from E. coli to apolipoprotein (apo) A-I in rabbits. In vitro incubation of rh-Met-proapo A-I with rabbit serum produced mature apo A-I3 isoproteins, as determined by the immunoblotting method. However, at the time we were unable to chemically confirm a newly produced protein band which appeared at the position of human apo A-I3. Since then, we have confirmed the amino acid sequence of the protein using a membrane protein sequence technique, and have concluded that it corresponds to human apo A-I3.