The invention relates to a method for producing polypeptides or proteins in a two-chain form by recombinant expression in E. coli host cells, whereby i) the polypeptide or protein exerts its biological activity as a two-chain polypeptide or protein, ii) the C-terminal amino acid group of the first chain is an Arg or Lys group, iii) the second chain of the protein/polypeptide, at its N terminus, has 1 to 20 amino acid groups and a pentapeptide sequence VPXGS referred to as PRS, wherein X may be any naturally occurring amino acid, wherein V represents Val, Leu, Ile, Ala, Phe, Pro or Gly, P represents Pro, Leu, Ile, Ala, Phe, Val or Gly, G represents Gly, Leu, Ile, Ala, Pro, Phe or Val and S represents Ser, Tyr, Trp or Thr.