Abnormal fractionation of beta-lactamase in Escherichia coli: evidence for an interaction with the inner membrane in the absence of a leader peptide.
beta-Lactamase with the -20 to -1 region of the leader peptide deleted (almost complete deletion of the leader peptide) [delta(-20,-1) beta-lactamase] was released from Escherichia coli cells by osmotic shock. Fractionation of the cells by conversion to spheroplasts and protease accessibility experiments further indicated that a portion of the protein may be bound to the cytoplasmic membrane and be partially exposed in the periplasmic space. Expression of delta(-20,-1) beta-lactamase conferred a 25-fold increase in the 50% lethal dose for ampicillin relative to that for controls, thus confirming that a small amount (about 2%) of the active protein is completely exported from the cytoplasm. These results suggest that even in the absence of a leader peptide, mature beta-lactamase is able to interact with the cytoplasmic membrane and be translocated into the periplasmic space, albeit with a low efficiency.
Bowden
G A
GA
Department of Chemical Engineering, University of Texas, Austin 78712.
Baneyx
F
F
Georgiou
G
G
D000667:Ampicillin / Q000494:pharmacology; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism*; D019286:Endopeptidase K; D004790:Enzyme Induction; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism*; D007928:Lethal Dose 50; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism; D013104:Spheroplasts / Q000737:chemistry; D013347:Subcellular Fractions / Q000737:chemistry; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
D021382:Protein Sorting Signals; D000667:Ampicillin; D012697:Serine Endopeptidases; D019286:Endopeptidase K; D001618:beta-Lactamases