Expression system for proteins

摘要

The invention provides a novel system for the tunable expression of nucleic acids encoding e.g., polypeptides such as recombinant proteins in prokaryotic systems. The system is based on the ability of T7 lysozyme (T7Lys) to inhibit the activity of T7RNAP. Expression of T7Lys can be continuously adjusted as its expression is under the control of a promoter whose activity can be titrated. The invention provides a host cell capable of expressing T7 RNA polymerase, the host cell comprising a first nucleic acid having a T7 lysozyme gene or a T7 lysozyme variant gene and a tunable promoter for controlling the expression of the T7 lysozyme gene. It also provides a host cell further comprising a second nucleic acid having a T7 promoter operably linked to a nucleic acid sequence encoding a target polypeptide, whereby expression of the target polypeptide is tuned via controlling the expression of the T7 lysozyme gene.