Translational fusion with a secretory enzyme as an indicator.

A novel type of translational fusion system has been developed by using a secretory protein, staphylococcal beta-lactamase, as an indicator. The beta-lactamase structural gene was modified to provide N-terminal extensions of 13 and 162 amino acids, and in both cases, the fusion protein was processed and the mature active enzyme was secreted; thus, the expression of a particular upstream gene can be analyzed by monitoring the beta-lactamase activity.