We are interested in understanding and engineering the interaction between cyclodextrins and proteins. Cyclodextrins are the natural ligands of specific proteins involved in carbohydrate metabolism, such as α-amylases or cyclo-/maltodextrin binding proteins. In these cases, the interaction occurs at particular substrate/product binding sites which have been shaped during evolution. However, due to their guest inclusion properties with small hydrophobic molecules, cyclodextrins also form complexes with amino-acid side chains on protein surfaces. The aromatic amino-acids, tryptophan, tyrosine and phenylalanine are the preferred guests and interaction with cyclodextrins (β-CD) necessitates partial solvent accessibility of these residues1. Binding constants are generally weak and do not directly correlate to accessible solvent area of these residues. Understanding the factors which control binding strength and specificity remains a challenge.
NOESY spectrum showing cross-peaks between β-cyclodextrin and TRP5 of unfolded chymotrypsin inhibitor 2. (From Aachmann et al, 2003).
This very property of cyclodextrins has proven its usefulness in increasing the solubility of polypeptides2, assisting in the folding of globular proteins3 (artificial chaperones) or inhibiting irreversible aggregation4. Hence, cyclodextrins are often used as stabilizers in pharmaceutical formulations of therapeutic peptides.
With current progress in the chemistry of cyclodextrins, polymers and protein engineering, it becomes possible to create new cyclodextrin-based materials for more specific and stronger binding to proteins. Such materials are being developed for diverse applications such as affinity chromatographic separation of proteins tagged with hydrophobic moieties5,6, protein immobilization in polymeric matrices for biosensing7, or design of protein nanopores for DNA sequencing8.
- Aachmann, F. L., Otzen, D. E., Larsen, K. L., Wimmer, R., 2003. Structural background of cyclodextrin-protein interactions. Protein Eng., 16, 905-912.
- Matilainen, L., Maunu, S. L., Pajander, J., Auriola, S., Jaaskelainen, I., Larsen, K. L., Jarvinen, T., & Jarho, P. (2009). The stability and dissolution properties of solid glucagon/gamma-cyclodextrin powder. Eur J Pharm Sci, 36, 412-420.
- Bajorunaite, E., Cirkovas, A., Radzevicius, K., Larsen, K. L., Sereikaite, J., & Bumelis, V. (2009). Anti-aggregatory effect of cyclodextrins in the refolding process of recombinant growth hormones from Escherichia coli inclusion bodies. Int J Biol Macromol, 44, 428-434.
- Otzen, D. E., Knudsen, B. R., Aachmann, F., Larsen, K. L., Wimmer, R., 2002. Structural basis for cyclodextrins' suppression of human growth hormone aggregation. Protein Sci., 11, 1779-1787.
- Nguyen, T., Joshi, N.S., Francis, M.B. 2006. An affinity-based method for the purification of fluorescently-labeled biomolecules. Bioconjugate Chem. 17, 869−872.
- Chung, JA, Wollack, JW, Hovlid, ML, Okesli, A, Chen, Y, Mueller, JD, Distefano, MD, Taton, TA, 2009. Purification of prenylated proteins by affinity chromatography on cyclodextrin-modified agarose. Anal Biochem. 386, 1-8.
- Fragoso, A., Sanromà, B., Ortiz, M., O'Sullivan, C.K., 2009. Layer-by-layer self-assembly of peroxidase on gold electrodes based on complementary cyclodextrin–adamantane supramolecular interactions. Soft Matter, 5, 400-406.
- Gu L-Q, Braha O, Conlan S, Cheley S, Bayley H, 1999. Stochastic sensing of organic analytes by a pore-forming protein containing a molecular adapter. Nature, 398:686–690.