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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.