Recombinantly produced hydrophobins from fungal analogues as highly surface-active performance proteins

• Published in: European biophysics journal Vol. 39; no. 3; pp. 457 - 468
• Main Authors: Wohlleben, Wendel, Subkowski, Thomas, Bollschweiler, Claus, von Vacano, Bernhard, Liu, Yaqian, Schrepp, Wolfgang, Baus, Ulf
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.02.2010; Springer-Verlag; Springer Nature B.V
• Subjects: Aspergillus nidulans; Bacillus subtilis; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Biochemistry; Biological and Medical Physics; Biomedical and Life Sciences; Biophysics; Calcium - chemistry; Cations, Divalent - chemistry; Cell Biology; Centrifuges; Cloning, Molecular; Elasticity; Emulsification; Escherichia coli; Fungal Proteins - chemistry; Fungal Proteins - genetics; Fungi; Fusion protein; Gene expression; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; hydrophobins; Ions; Kinetics; Life Sciences; Mechanical properties; Membrane Biology; Molecular structure; Nanotechnology; Neurobiology; Oligomerization; Original Paper; Protein Multimerization; Proteins; Recombinant Fusion Proteins - chemistry; Self-association; Sodium - chemistry; Solutions; Surface-Active Agents - chemistry; Surfactants; Temperature; Ultracentrifugation; Hydrophobin; Emulsion; Self-association; Analytical ultracentrifugation; Interface elasticity; Recombinant
• DOI: 10.1007/s00249-009-0430-4
• ISSN: 0175-7571

Hydrophobins are available from natural resources only in milligram amounts. BASF succeeded in a recombinant production process, up-scaled to pilot plant production in kilogram scale. Strain and protein optimization by modulation of gene expression and generation of fusion proteins finally leads to two class I hydrophobins called H*Protein A and H*Protein B. By analytical ultracentrifugation, we confirm that the self-association of H*Proteins in solution is governed by their sequence, because oligomerization is induced by the same mechanisms (pH > 6, temperature ≫ 5°C, concentration > 0.2 mg/ml) as for the well-known native hydrophobins SC3 and HFB II. Additionally, we established the triggering of structure formation by bridging with divalent ions and the stabilization of dimers and tetramers by monovalent ions or surfactants. This interplay with surfactants can be exploited synergistically: The capacity for emulsification of a 300 ppm standard surfactant solution is boosted from 0 to 100% by the addition of a mere 1 ppm of our new hydrophobins, with H*Protein A and H*Protein B having specific application profiles. This astonishing performance is rationalized by the finding that the same minute admixtures enhance significantly the interfacial elastic modulus, thus stabilizing interfaces against coalescence and phase separation.