Which heterologous protein expression systems allow for the post-translational modifications of the recombinant proteins? Solution Yeast systems are generally regarded as safe heterologous recombinant (suitable for DNA recombination) system for the expression of proteins via heterologous expression (Saccharomyces cerevisiae). This yeast is unicellular eukaryotic system & its secretory pathway has associated with N-terminal signal sequences such as Pho5, Suc2 for post translational and co-translational modifications of secretory recombinant proteins (obtained through recombinant DNA expression) in endoplasmic reticulum. The post-translational modification can be done through \"signal peptidases\" & N-linked and O-linked (to serine/threonine) glycosylation..