THE BACILLUS-SUBTILIS LIPOPROTEIN LPLA CAUSES CELL-LYSIS WHEN EXPRESSED IN ESCHERICHIA-COLI

A gene called lplA (lipoprotein-like) has been isolated from a genomic library of Bacillus subtilis expressed in Escherichia coli. Clones ca rrying the lplA gene were selected by the ability of the colonies to g ive visible haloes of starch hydrolysis. The cloned fragment contains an open reading frame (ORF) of 1509 bp encoding a protein of 56 kDa. T he protein contains a typical N-terminal signal sequence, a putative t ransmembrane anchor domain and a leucine zipper at the C-terminus. The expression of this protein in E. coli causes cell lysis, only the N-t erminal domain of the LplA protein being responsible for this phenotyp e. The mechanism of cell lysis is similar to that previously suggested for the expression in E. coli of the lipoproteins encoded by the Stre ptococcus pneumoniae genes malX and amiA. The protein is modified with palmitic acid when secreted in E. coli, confirming that it is a typic al lipoprotein.