Biophysical Society Thematic Meeting - October 13-15, 2015

Biophysics of Proteins at Surfaces: Assembly, Activation, Signaling

Tuesday Speaker Abstracts

Supramolecular Assembly of Pulmonary Surfactant Protein SP-B Ensures Proper Dynamics and Structural Stability of Multilayered Films at the Respiratory Air-Liquid Interface Bárbara Olmeda 1 , Begoña García-Álvarez 1 , Manuel J. Gómez 2 , Marta Martínez-Calle 1 , Antonio Cruz 1 , Jesús Pérez-Gil 1 . 1 Universidad Complutense de Madrid, Madrid, Spain, 2 Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, Madrid, Spain. Surfactant protein SP-B is essential to facilitate the formation and proper performance of surface active pulmonary surfactant films at the air-liquid interface of mammalian lungs, allowing both dynamics and mechanical stability of the film. Despite its importance, neither a structural model nor a molecular mechanism of SP-B is available. In the present work we have purified and characterized native SP-B supramolecular assemblies to elaborate a model that supports structure-function features described for SP-B. Purification of porcine SP-B using detergent-solubilized surfactant reveals the presence of 10 nm ring-shaped particles. These rings, observed by atomic force and electron microscopy, would be assembled by oligomerization of SP-B as a multimer of dimers forming a hydrophobically coated ring at the surface of phospholipid membranes or monolayers. Docking of rings from neighboring membranes would lead to formation of SP-B-based hydrophobic tubes, competent to facilitate the rapid flow of surface active lipids both between membranes and between surfactant membranes and the interface. The existence of these SP-B complexes not only sustain the dynamic behavior required by breathing conditions, but also explain how the protein facilitates cohesivity and mechanical stabilization of the multilayered three-dimensional structure of surfactant films at the surface of the alveolar epithelium.

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