Synthesis and Purification of Mature Human Serum Albumin from E. Coli

Significant synthesis of Human Serum Albumin (HSA) was demonstrated in E. coli using efficient bacterial expression signals. The recombinant HSA is produced essentially as an insoluble aggregate and differs from natural HSA by the presence of a methionine at the N-terminus. However, the Met-HSA could be re-natured, purified and was found to be very similar to the natural protein. A procedure was devised to produce mature HSA starting with the authentic N-terminal sequence from E. coli. By analogy with the maturation of the HSA propeptide, a plasmid expressing a fusion between the first six residues of the bacteriophage λcII protein (Val-Arg-Ala-Asn-Lys-Arg-) and the sequence of mature HSA was constructed. After renaturation, this fusion protein was cleaved by trypsin in vitro to yield a mature refolded HSA with native N-terminal sequence. This protein could not be distinguished by several criteria from authentic natural HSA.