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Comparative Study
. 1996 Jun 1;238(2):418-22.
doi: 10.1111/j.1432-1033.1996.0418z.x.

Purification of Escherichia coli pro-haemolysin, and a comparison with the properties of mature alpha-haemolysin

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Free article
Comparative Study

Purification of Escherichia coli pro-haemolysin, and a comparison with the properties of mature alpha-haemolysin

A Soloaga et al. Eur J Biochem. .
Free article

Abstract

Pro-haemolysin (approximately 110 kDa), the inactive precursor of the membrane-lytic toxin alpha-haemolysin, has been purified from an overproducing strain of Escherichia coli. Pro-haemolysin forms aggregates in aqueous media, like the mature protein, suggesting an amphipathic structure. Direct measurements of protein binding to liposomal membranes, following a novel procedure, show that pro-haemolysin can bind the lipid bilayers to a similar extent as alpha-haemolysin. This is confirmed by the observed changes in the intrinsic fluorescence emission of the protein upon binding the bilayers. However, pro-haemolysin is totally unable to induce liposomal membrane lysis. Binding of Ca2+, that is essential for the lytic activity of alpha-haemolysin, is greatly diminished in the precursor protein, as shown both by direct measurements of 45Ca(2+)-binding and by fluorescence measurements. The results suggest that binding of a fatty acyl residue in the activation step brings about an important conformational change in the protein that involves the Ca(2+)-binding domain.

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