Fig. 1
From: Engineered mosaic protein polymers; a simple route to multifunctional biomaterials
Production of mosaic Caf1 polymers by E. coli. In this diagram, E. coli have been transformed with the pT7-COP plasmid, which contains the caf1 operon with a caf1 subunit “A” gene (caf1SubA, blue), and a pBad plasmid containing a caf1 subunit “B” gene (caf1SubB, yellow) under the control of an arabinose inducible promoter. When arabinose is added to cells growing in culture at 35 °C, both the caf1 operon and the additional subunit genes are expressed. Subunits are exported to the periplasm where they are bound by the chaperone, Caf1M (green). Caf1M delivers the subunits to the outer membrane usher, Caf1A (tan), which assembles the subunits into a polymer. Both subunits have been detected in the extracellular fraction of cell cultures expressing both genes, but it was not known whether they form a mosaic homopolymer containing a mixture of the two subunits (Caf1SubA:SubB, top), or two separate homopolymers (Caf1SubA and Caf1SubB, bottom). Caf1 polymer models were prepared from the Caf1:Caf1:Caf1M crystal structure (PDB: 1P5U), and visualised using the CCP4MG software package [50]