Effect of upstream translation in a synthetic two-cistron system encoding Endo-1, 4-β-glucanase and β-glucosidase

Effect of upstream translation on the production of β-glucosidase, product of the second cistron, was examined in our two-cistron system. When the space between the termination codon of the first cistron and the initiation codon of the second cistron was increased from 50 base pairs to 1055 base pairs, the production of β-glucosidase was reduced from 22% to 14%. The coupled translation in the two-cistron system was further supported by the fact that even without the Shine-Dalgarno (SD) sequence for the second cistron a little amount of β-glucosidase was produced when the distance between the two genes was 17 base pairs, but β-glucosidase was not detectable when the second gene was separated from the first gene by 1022 base pairs. These results demonstrate that translation of the second cistron in our synthetic two-cistron system occurred by two factors, the SD sequence and continuous flow of the ribosomes.