Membrane interactions of Ocellatins. Where do antimicrobial gaps stem from?

Publication year: 2021
Authors: J.Muñoz‑López 1,2, J.C.L.Oliveira 1, D.A.G.R. Michel 3, C.S. Ferreira 3, F.Gomes Neto 4, E.S.Salnikov 2, R.M.Verly 3, B.Bechinger 2,5, J.M.Resende 1

1 - Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, P.O. Box 486, Belo Horizonte, MG 31270‑901, Brazil
2 - UMR7177, Institut de Chimie, Université de Strasbourg/CNRS, 4, rue Blaise Pascal, 67000 Strasbourg, France
3 - Departamento de Química, Universidade Federal Dos Vales do Jequitinhonha e Mucuri, Diamantina, MG 39100‑000, Brazil
4 - Laboratório de Toxinologia, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro 21040‑900, Brazil
5 - Institut Universitaire de France, 75005 Paris, France

Published in: Amino Acids, Vol. 53, p. 1241–1256 (2021)
doi: 10.1007/s00726-021-03029-0

The antimicrobial peptides Ocellatin-LB1, -LB2 and -F1, isolated from frogs, are identical from residue 1 to 22, which correspond to the -LB1 sequence, whereas -LB2 carries an extra N and -F1 additional NKL residues at their C-termini. Despite the similar sequences, previous investigations showed different spectra of activities and biophysical investigations indicated a direct correlation between both membrane-disruptive properties and activities, i.e., ocellatin-F1 > ocellatin-LB1 > ocellatin-LB2. This study presents experimental evidence as well as results from theoretical studies that contribute to a deeper understanding on how these peptides exert their antimicrobial activities and how small differences in the amino acid composition and their secondary structure can be correlated to these activity gaps. Solid-state NMR experiments allied to the simulation of anisotropic NMR parameters allowed the determination of the membrane topologies of these ocellatins. Interestingly, the extra Asn residue at the Ocellatin-LB2 C-terminus results in increased topological flexibility, which is mainly related to wobbling of the helix main axis as noticed by molecular dynamics simulations. Binding kinetics and thermodynamics of the interactions have also been assessed by Surface Plasmon Resonance and Isothermal Titration Calorimetry. Therefore, these investigations allowed to understand in atomic detail the relationships between peptide structure and membrane topology, which are in tune within the series -F1 >  > -LB1 ≥ -LB2, as well as how peptide dynamics can affect membrane topology, insertion and binding.

MP-SPR keywords: membrane affinity, peptide-membrane interaction, SiO2 sensor slide