StAsp-PSI affects the structure of phospholipids during its interaction with biomembranes.

FERNANDO F. MUÑOZ, ; MARÍA F. PALOMARES,; GUSTAVO R. DALEO, ; JOSÉ VILLALAÍN ; MARÍA G. GUEVARA.

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB).; 2011

Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB).

We have reported the ability of the swaposin domain of potato aspartic proteases ( Asp-PSI) to produce leakage in vesicle membranes containing anionic phospholipids. However, the mode that Asp-PSI perturbs the structure of lipidic bilayers is not well understood. Here, we examined the effect of Asp-PSI on the structural and thermotropic properties of the major phospholipid types of bacterial and animal cells. Results obtained from the steady-state fluorescence anisotropy of the probe DPH showed that Asp-PSI was able to perturb the lipid acyl chains in anionic membranes, composed of DMPG, DMPS and DMPA. The protein also caused a change in the anisotropy on DMPA vesicles using TMA-DPH probe, suggesting a perturbation of the lipid headgroups. Results obtained from differential scanning calorimetry showed that Asp-PSI was able to disturb bilayers composed of DMPG and DMPS. The main thermal transition of the lipids was associated with two peaks, which should be due to mixed phases, indicating that one of them would be enriched in Asp-PSI whereas the other one would be impoverished in it. The results suggest that the difference in charge between the lipid headgroups affects the Asp-PSI incorporation into the lipid bilayer, and therefore it could be suggested that the protein should be primarily located at the lipid-water interface, influencing the fluidity of the phospholipids.