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An E. coli expression system which detoxifies the HIV protease.

Based on a variety of independent assays, the expression of HIV (human immunodeficiency virus type 1) protease in living bacterial cells results in their loss of viability. Although the mechanism is not proven, we have observed degradation of cellular proteins in E. coli expressing large amounts of active HIV protease. In order to avoid the loss of viability, we devised an expression system in which the viral protease is fused to beta-lactamase and is rapidly secreted to the periplasmic space, thus reducing its duration in the cytosol. Furthermore, we find the periplasmic form of the protease is soluble and enzymatically is several-fold more active than enzyme recovered from intracellular aggregates. The question of whether the viral protease may be toxic to infected cells is discussed.