Membrane proteins constitute a large and important fraction of the proteome, with 80% of the druggable targets in cells being membrane proteins. The holotranslocon, a large transmembrane multiprotein complex comprising seven subunits catalyzes the entry of proteins into cell membranes. EMBL and UK based scientists used the MultiColi™ expression system in the ComplexINC R&D consortium to engineer a tightly regulated multigene co-expression circuit which enabled the functional assembly of holotranslocon complex published in the early edition of the Proceedings of the National Academy USA.