Analysis of λ receptor and β-lactamase synthesis and export using cloned genes in a minicell system

Abstract

We have cloned lamB, the gene for λ receptor (an outer membrane protein), on a small plasmid which also carries the gene for β-lactamase (a periplasmic protein). We have identified a promoter in the region of malK, the gene immediately preceding lamB, which is active in minicells but relatively inactive in vitro. Using a minicell system, we have found that both λ receptor and β-lactamase are made as full length precursors which are subsequently processed. We also show that the λ receptor precursor can be exported to the outer membrane before it is processed. Mature β-lactamase is found only in the periplasm, suggesting that processing may be a requirement for export to the periplasm.