Fig. 2: Localized protein synthesis by coupled gene expression machines on single DNA molecules.

a Surface-immobilized DNA encoding the ht gene with strong recognition sites for transcription (RNAP) and translation (ribosome) machines from cell lysate (TxTl). The cell lysate and fluorogenic dye were introduced to the DNA under constant flow through a flow channel in an open microfluidic chip. The length of the C-terminal extension fused to the ht gene was varied (ΔL), tuning the residence time of HT proteins on DNA. b Fluorescent images of the HT signal at the end of expression experiments for the three corresponding extension lengths indicated in d. Scale bar, 5 µm. c The number of expression spots as a function of C-terminal extension length. Experiments were replicated with increasing C-terminal extension length for n = 2,2,3,2 (small circles) to obtain average values (large circles). The error bar is given as SD. The gray line is fit to the data with a logistic function and L₀ as the midpoint. d Examples of protein synthesis traces with the three different nucleotides (nt) extension lengths. e Intensity distributions of expression spots over the ensemble corresponding to constructs in d. The black bars indicate the background signal. Source data are provided as a Source Data file.