Inhibition of Serratia marcescens nuclease secretion by a truncated nuclease peptide

The production of extracellular nuclease (Nuc) from the Serratia marcescens nucA chromosomal locus is inhibited in cells producing the N-terminal portion of Nuc from a multicopy plasmid. This inhibition in trans is not at the level of nucA expression, but rather at the level of secretion of the Nuc protein. Production of the periplasmic protein β-lactamase (B1a) does not inhibit Nuc production unless fused to the nucA signal peptide and expressed from nucAp. Inhibition by either the truncated Nuc peptide (ΔNuc) or a B1a fusion protein is promoter specific and observed when expressed from nucAp; little inhibition is observed when the same protein is expressed from the lacZpo promoter-operator. This promoter specificity is also true for the secretion of Nuc itself.