Interaction of biologically-relevant peptides with membrane model systems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

In this work, we monitor the alterations caused in membrane model systems upon the addition of biologically-relevant peptides. Our first study reports on the interaction with model membranes of an internal fusion peptide (SARSIFP) from the S2 subunit of the SARS coronavirus spike glycoprotein. It is believed that SARSIFP might be fundamental for the later steps of the fusion between the viral and host cellular membranes. Non-linear least-squares fits of stearic acid spin labels ESR spectra showed that the rotational dynamics of the HPS headgroup region and of the whole carbon chain of SDS surfactants was perturbed by the peptide. Additionally, Tyr fluorescence quenching promoted by spin labels locates this residue in the aqueous interface of HPS and in the hydrophobic core of SDS micelles. The second investigation deals with the conformational changes induced by interactions with model membranes of three TOAC-labeled peptide analogues derived from a new antimicrobial peptide extracted from the skin secretion of the frog Hypsiboas albopunctatus. Our results shed light on how the peptides labeled at positions 0, 2, and 13 interact with DPPC/DPPA/X (X = DPPE, SM, and CL) liposomes and LPC micelles. The findings allowed the description of the peptide topology into the membrane, where the N-terminal region is solvent-exposed, position 2 is at the interface, and position 13 is fully inserted