Analysis of lambda receptor and beta-lactamase synthesis and export using cloned genes in a minicell system

Summary We have cloned lamB, the gene for receptor (an outer membrane protein), on a small plasmid which also carries the gene for -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 receptor and -lactamase are made as full length precursors which are subsequently processed. We also show that the receptor precursor can be exported to the outer membrane before it is processed. Mature -lactamase is found only in the periplasm, suggesting that processing may be a requirement for export to the periplasm.