Translational regulation of a recombinant operon containing human platelet-derived growth factor (PDGF)-encoding genes in Escherichia coli: genetic titration of the peptide chains of the heterodimer AB.

A new strategy is described for the production of recombinant heteromultimeric proteins using Escherichia coli as host. A recombinant operon was constructed containing modified cDNA sequences encoding the mature A and B chains of human platelet-derived growth factor (PDGF). The relative expression rates of the PDGF genes were varied over a range equivalent to A:B ratios from 0.8 to 3.7 by means of translational regulation. This was achieved using two different translational initiation sequences (TIS) upstream from the respective coding regions, one derived from the E. coli atpE translational initiation region, and the other containing a sequence with extended complementarity to the 3' end of the 16S rRNA. The generation of mature PDGF A and B chains in different relative amounts in E. coli provided the basis for developing a novel procedure for the production of the biologically active PDGF heterodimer AB in large quantities. The general strategy is applicable to the preparation of a wide range of heteromultimeric complexes. Moreover, the described PDGF operon constitutes a compact and versatile model system for studies of the posttranscriptional regulation of gene expression.