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EPRC is a leading institute in Europe for comparative research on public policy, with a particular focus on regional development policies. Spanning 30 European countries, EPRC research programmes have a strong emphasis on applied research and knowledge exchange, including the provision of policy advice to EU institutions and national and sub-national government authorities throughout Europe.

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Silica condensation by a silicatein alpha homologue involves surface-induced transition to a stable structural intermediate forming a saturated monolayer

Patwardhan, Siddharth V. and Holt, Stephen A. and Kelly, Sharon M. and Kreiner, Michaela and Perry, Carole C. and van der Walle, Christopher F. (2010) Silica condensation by a silicatein alpha homologue involves surface-induced transition to a stable structural intermediate forming a saturated monolayer. Biomacromolecules, 11 (11). pp. 3126-3135. ISSN 1525-7797

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Abstract

Silicatein alpha exists within the protein filament of silica spicules of the marine sponge Tethya aurantium in a predominantly beta-sheet structure. However, it is produced in a soluble form with mixed alpha-helix/beta-sheet structure akin to its cathepsin L homologue. To understand this conformational transition in the context of enzyme catalyzed silica condensation, we used a functional, recombinant silicatein alpha termed 4SER. In solution, 4SER becomes conformationally unstable at pH 7 and readily unfolds to a soluble beta-sheet intermediate, losing the majority of its helical structure. This beta-sheet intermediate is present following adsorption of 4SER to a silica surface from solution. 4SER is particularly surface active, forming a near saturated monolayer on SiO2 from low bulk concentrations, without transition to multilayers at high bulk concentrations. The adsorbed intermediate remains stable during silica condensation and drying. We propose that the beta-sheet structure for silicatein a. in marine sponge spicules represents a stable structural intermediate, formed upon adsorption to the silica surface.