Modular design of synthetic redox and light-absorbing proteins
Rau, H.K., DeJonge, N., Hörth, P., Snigula, H., Scheer, H., Haehnel, W.
Institut für Biologie II/Biochemie, Albert-Ludwigs-Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany
An approach to de novo proteins with cofactor binding sites is the design of alpha-helical bundles capable of binding heme, chlorophyll or other groups. Chemoselective binding of alpha-helical peptides to predetermined positions of a cyclic peptide template [1] overcomes the problem of protein folding and association of single helices, and increases the stability. We have
synthesized de novo designed redox proteins with high structural complexity and defined topology [2]. One of these synthetic proteins contains 128 residues and accommodates two bis-histidine ligated heme groups. This realizes a water soluble model of the cytochrome b core with two parallel heme-binding helices alternating with two antiparallel helices shielding the two hydrophobic heme binding sites. Characterization by mass spectrometry and circular dichroism support the anticipated structure. Coupling of the synthetic protein to a gold electrode by cysteamine linkers enabled a direct electron transfer from the electrode to the heme groups and then to adsorbed nitrate reductase, resulting in enzyme catalyzed nitrate reduction. In a modular approach we have also synthesized different types of redox proteins by coupling different helices to the fourth site of a common three helices carrying template. These include proteins with a heme group, a heme group plus a covalently attached Ru(bpy)3 and different amino acid residues in the hydrophobic interior. A light-induced electron transfer was measured.
[1] Mutter, M., Altmann, K.-H., Hersperger, R., Koziej, P., Nebel, K., Tuchscherer, G. and Vuilleumier, S. (1988) Helv. Chim. Acta 71, 835.
[2] Rau, H. and Haehnel W. (1998) J. Am. Chem. Soc., in press.
| LOCATION |
DATE |
TIME |
| Lecture Hall II |
Sunday, April 5 |
06:00 pm |