In Escherichia coli, the Twin-arginine (Tat) secretion system is one of the main routes of the protein export to the periplasm. The Tat pathway secretes a set of proteins with important physiological functions. In our study, we investigated the influence of the deactivation of the Tat pathway on the E. coli cells. We applied a comprehensive and comparative proteomic analysis of the E. coli wild type and tat mutant. This dataset provides mass spectrometry based details on the abundances of proteins in cytoplasmic, periplasmic and membrane fractions. We observed that a tat deletion increases abundances of proteins involved in protein folding, degradation, responses to heat, oxidation, osmolarity, and cold. Moreover, the impairment of E. coli outer membrane resulted in the activation of proteins responsible for cell wall biogenesis. The tat deletion negatively affects the synthesis of iron transporters and imbalances its homeostasis in the cell.