A translation-coupling DNA cassette for monitoring protein translation in Escherichia coli

► A mRNA secondary structure was designed to couple translation of two genes. ► System was successfully demonstrated with reporter genes and resistance markers. ► Translational coupling functions at high, medium, and low expression levels. ► Translational coupling generates a proportional translation response. ► The system was used to optimize conditions for expressing a ∼300 kDa protein.