Binding studies of antimicrobial lipopeptide Bacillomycin D homologues to model membranes with varying sterol content

CARLOS MUÑOZ-GARAY; SATHISHKUMAR MUNUSAMY; AGUSTIN LUNA BULBARELA; ROMINA VAZQUEZ; VANESA HERLAX; SABINA MATÉ; LEOBARDO SERRANO CARREON

Puebla

Congreso; XX Congreso de Bioenergética y Biomembranas; 2017

Sociedad Mexicana de Bioquímica

This study was designed to examine the interactions between Bacillomycin D homologues and model membranes of different sterol content. Bacillomycin D homologues are cyclic lipopeptides containing seven α-amino acids and a β-amino fatty acid linked by amide bond to the constituent amino acid residue. Among several Bacillomycin D homologues, the ones containing C14 (BC14) and C16 (BC16) β-amino fatty acids are believed to have more antifungal activity.In this context, we studied lipopeptide-lipid interactions through of follow experimental models: Langmuir-monolayer, spectrofluorometry (using the intrinsic fluorescence of a tyrosine residue present in the lipopeptides and their quenching by acrylamide) and calcein release from large unilamellar vesicles (LUV). The membrane models were composed by PC:Chol, PC:Erg or PCand exploring the interaction of both lipopetides with each experimental model.Results obtained from all models, PC:Erg membrane composition show the best condition to lipopeptide insertion in membrane and of two tested isoforms, BC16 shows the best activity. In calcein release assay dose-response to ergosterol was established. Two calcein releasing kinetics were presented as a function of lipopeptide concentration, suggesting different membrane interaction processes. Langmuir-monolayer studies, we explored the capacity of Bacillomycin itself to form monolayers at air-water interfaces and isothermal compression was obtained. In this system PC:Erg composition showed lipopeptide insertion on high lateral membrane pressure, not so in the other mixtures. Further binding information was obtained by quenching experiments with acrylamide, accessibility to tyrosine was reduced considerably when the CB16 is incubated with PC:Erg LUVs. In summary, our results showed that both lipopeptides have stronger interactions with POPC:ergosterol membranes being BC16 more active than BC14.