Abstract
Functional amyloids have been identified in a wide range of organisms, taking on a variety of biological roles and being controlled by remarkable mechanisms of directed assembly. Here, we report that amyloid fibrils constitute the ribs of the buoyancy organelles of Anabaena flos-aquae. The walls of these gas-filled vesicles are known to comprise a single protein, GvpA, arranged in a low pitch helix. However, the tertiary and quaternary structures have been elusive. Using solid-state NMR correlation spectroscopy we find detailed evidence for an extended cross-β structure. This amyloid assembly helps to account for the strength and amphiphilic properties of the vesicle wall. Buoyancy organelles thus dramatically extend the scope of known functional amyloids.
Background: The gas vesicles of aquatic microorganisms are hollow proteinaceous shells with remarkable physical properties that enable them to function as floatation organelles.
Results: The gas vesicle subunits associate in a cross-β arrangement.
Conclusion: The gas vesicle wall constitutes a functional amyloid.
Significance: This new category of functional amyloid broadens our understanding of the diverse roles of the amyloid fold.