Biophysical Society Thematic Meeting - October 25-30, 2015

Polymers and Self Assembly: From Biology to Nanomaterials Poster Session I

34-POS Board 34 pH Dependent Peptide Self-Assemblies: A Mechanism as Old as Viruses Maité Paternostre 2 , Celine Valéry 1 , Deville-Foillard Stéphanie 2 , Cristelle Meriadec 3 , Pierre Legrand 4 , Stéphane Bressanelli 2 , Marie-Hélène Ledu 2 , Franck Artzner 3 . 2 Institute of integrative Biology of the celle, Gif-sur-Yvette, 91191, France, 1 Ipsen, Les Ulis, 91940, France, 3 Institut de Physique de Rennes, Rennes, 35042, France, 4 Synchrotron SOLEIL, Gif sur Yvette, 91190, France. External stimuli are powerful tools that naturally control protein assemblies and functions. For example during viral entry and exit changes in pH are known to trigger large protein conformational changes. However, the molecular features stabilising the higher pH structures remain unclear. We report on a decapeptide that self-assembles into either 50nm diameter nanotubes at high pH or 10.7nm diameter nanotubes at low pH. To solve both low and high pH structures we combine complementary technical approaches going from X-ray crystallography, fiber diffraction and vibrational spectroscopy to electron and optical microscopies to have access from the smallest (sub-angstöm) to highest (micometers) level of organization. The peptide conformation switches from a globular one at pH>7.5 to an extended one at pH<6.5. The high pH crystal structure obtained at 0.85Å resolution reveals a histidine-serine H-bond and histidine- aromatic interactions, whereas the low pH molecular structure demonstrates these key interactions have disappeared, likely in favour of cation-π proximities. Interestingly, re-analysing protein structures with pH-dependent functions reveals that these specific interaction networks are present in viral, bacterial and human proteins. The mechanism discovered in this study may thus be generally used by pH-dependent proteins and opens new prospects in the field of nanomaterials.

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