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Membrane binding and oligomer formation by the calcium-dependent lipopeptide antibiotic A54145: a quantitative study with pyrene excimer fluorescence

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Date

2016-09-20

Authors

Zhang, TianHua
Taylor, Scott D.
Palmer, Michael
Duhamel, Jean

Journal Title

Journal ISSN

Volume Title

Publisher

Elsevier

Abstract

A54145 is a lipopeptide antibiotic related to daptomycin that permeabilizes bacterial cell membranes. Its action requires both calcium and phosphatidylglycerol in the target membrane, and it is accompanied by the formation of membrane-associated oligomers. We here probed the interaction of A54145 with model membranes composed of dimyristoylphosphatidylcholine and dimyristoylphosphatidylglycerol, using the steady-state and time-resolved fluorescence of a pyrene-labeled derivative (Py-A54145). In solution, the labeled peptide was found to exist as a monomer. Its membrane interaction occurred in two stages that could be clearly distinguished by varying the calcium concentration. In the first stage, which was observed between 0.15 and 1 mM calcium, Py-A54145 bound to the membrane, as indicated by a strong increase in pyrene monomer emission. At the same calcium concentration, excimer emission increased also, suggesting that Py-A54145 had oligomerized. A global analysis of the time-resolved pyrene monomer and excimer fluorescence confirmed that Py-A54145 forms oligomers quantitatively and concomitantly with membrane binding. When calcium was raised beyond 1 mM, a distinct second transition was observed that may correspond to a doubling of the number of oligomer subunits. The collective findings confirm and extend our understanding of the action mode of A54145 and daptomycin.

Description

The final publication is available at Elsevier via http://doi.org/10.1016/j.bpj.2016.07.018 © 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

Keywords

Excimer fluorescence, Solvent polarities, Py Scale, Daptomycin, Polymer, Model, Macromolecules, Association, Transitions, Inhibition

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Citation

URI

https://doi.org/10.1016/j.bpj.2016.07.018
 http://hdl.handle.net/10012/11715

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Waterloo Research
Chemistry