1887

Abstract

Summary: The requirement for the activation of phospholipase A by the colicin A lysis protein (Cal) in the efficient release of colicin A by cells containing colicin A plasmids was studied. In particular, we wished to determine if this activation is the primary effect of Cal or whether it reflects more generalized damage to the envelope caused by the presence of large quantities of this small acylated protein. cells, which were shown to be leaky for periplasmic proteins, were transduced to and then transformed with the recombinant colicin A plasmid pKA. Both the and strains released large quantities of colicin A following induction, indicating that in these cells phospholipase A activation is not required for colicin release. This release was, however, still dependent on a functioning Cal protein. The assembly and processing of Cal in the cell envelope was studied by combining pulse-chase labelling with isopycnic sucrose density gradient centrifugation of the cell membranes. Precursor Cal and lipid-modified precursor Cal were found in the inner membrane at early times of chase, and gave rise to mature Cal which accumulated in both the inner and outer membrane after further chase. The signal peptide was also visible on these gradients, and its distribution too was restricted to the inner membrane. Gradient centrifugation of envelopes of cells which were overproducing Cal resulted in very poor separation of the membranes. The results of these studies provide evidence that the colicin A lysis protein causes phospholipase A-independent alterations in the integrity of the envelope. These alterations are required for the breakdown of the permeability barrier leading to colicin export.

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/content/journal/micro/10.1099/00221287-137-1-81
1991-01-01
2019-11-19
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http://instance.metastore.ingenta.com/content/journal/micro/10.1099/00221287-137-1-81
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