PMP1 18-38, a yeast plasma membrane protein fragment, binds phosphatidylserine from bilayer mixtures with phosphatidylcholine: a (2)H-NMR study.

PMP1 is a 38-residue plasma membrane protein of the yeast Saccharomyces cerevisiae that regulates the activity of the H(+)-ATPase. The cytoplasmic domain conformation results in a specific interfacial distribution of five basic side chains, thought to strongly interact with anionic phospholipids. We have used the PMP1 18-38 fragment to carry out a deuterium nuclear magnetic resonance ((2)H-NMR) study for investigating the interactions between the PMP1 cytoplasmic domain and phosphatidylserines. For this purpose, mixed bilayers of 1-palmitoyl, 2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl, 2-oleoyl-sn-glycero-3-phosphoserine (POPS) were used as model membranes (POPC/POPS 5:1, m/m). Spectra of headgroup- and chain-deuterated POPC and POPS phospholipids, POPC-d4, POPC-d31, POPS-d3, and POPS-d31, were recorded at different temperatures and for various concentrations of the PMP1 fragment. Data obtained from POPS deuterons revealed the formation of specific peptide-POPS complexes giving rise to a slow exchange between free and bound PS lipids, scarcely observed in solid-state NMR studies of lipid-peptide/protein interactions. The stoichiometry of the complex (8 POPS per peptide) was determined and its significance is discussed. The data obtained with headgroup-deuterated POPC were rationalized with a model that integrates the electrostatic perturbation induced by the cationic peptide on the negatively charged membrane interface, and a "spacer" effect due to the intercalation of POPS/PMP1f complexes between choline headgroups

From bulk to plasmonic nanoparticle surfaces: The behavior of two potent therapeutic peptides, octreotide and pasireotide

14 págs.; 10 figs.; 2 tabs.Octreotide and pasireotide are two cyclic somatostatin analogues with an important clinical use in the treatment and diagnosis of neuroendocrine tumors. Herein, by the combined use of several techniques (UV-visible absorption, fluorescence, circular dichroism, ζ-potential, transmission electron microscopy, Raman scattering, surface-enhanced Raman scattering, and quantum mechanical calculations) we have followed the structural dynamics of these analogues in the bulk, as well as their binding sites on plasmonic (gold and silver) colloids. In contrast to the previously derived conclusions, the two peptides seem to possess completely different conformational features. Octreotide, a cyclic octapeptide, is formed by a moderately flexible type-II′ β-turn maintained by a deformable disulfide linkage. Pasireotide, in which the cyclic character is made possible by peptide bonds, manifests a rigid backbone formed by two oppositely placed tight turns of different types, i.e. γ-turn and type-I β-turn. Owing to their cationic character, both analogues induce aggregation of negatively charged gold and silver colloids. Nevertheless, despite their notable structural differences, both peptides bind onto gold nanoparticles through their unique d-Trp residue. In contrast, their binding to silver colloids seems to be of electrostatic nature, as formed through monodentate or bidentate ionic pairs. © the Owner Societies 2016The authors would like to thank Novartis Pharma (Basel, Switzerland) for generously providing the lyophilized sample of pasireotide. This work was granted access to the HPC resources of IDRIS (Orsay, France) under the allocations c2016085065 by GENCI (Grand Equipement National de Calcul Intensif). A. C. was supported by a Pasteur Innov (PIV15-197) and a PTR grant (PTR451) from Institut Pasteur. S. S. C. acknowledges the Spanish Ministerio de Economia y Competitividad for the project FIS2014-52212-R.Peer Reviewe

Chemical synthesis of a fluorescent IGF-II analogue

Insulin-like growth factor II (IGF-II) is a protein with high structural and sequence similarity to insulin. Unlike insulin, it binds both the type 1 IGF receptor and the exon 11- isoform of the insulin receptor with high affinity. The overexpression and up regulation of IGF-II has been associated with the progression of various forms of cancer. The exact binding mechanism of IGF-II to its high affinity receptors is still not completely understood. Herein we describe the successful synthesis of a novel fluorescent IGF-II protein (F19Cou IGF-II), where residue 19 (phenylalanine) has been replaced by a fluorescent chromophore (coumaryl glycine). This novel coumaryl IGF-II analogue will be a useful tool for analysing the receptor interaction mechanisms in future studies.Jade M. Cottam, Denis B. Scanlon, John A. Karas, Antonio N. Calabrese, Tara L. Pukala, Briony E. Forbes, John C. Wallace, Andrew D. Abel