Template-mediated N-to-C-terminal assembly of peptide chains and cyclic peptides on programmable heterodimeric coiled-coil scaffolds

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Most biochemical processes in organisms are mediated by proteins such as enzymes and multi-protein complexes. None of the state-of-the-art catalysts can compete with the biological synthesis machineries in terms of efficiency and selectivity. Protein function is directed by the three dimensional structure which is based on the underlying amino-acid sequence. Exploring sequence-to-structure-to-function relationships is not only fundamental to our understanding of the function of known proteins but also the basis for the design of new functional proteins and peptides.Simple sequence-to-structure-relationships are understood for the beta-strand, the alpha-helical coiled coil, the collagen triple helix and in part for the zinc-finger motif and the WW-domain. However, these few folding motifs cover properties such as controlled oligomerisation and association as well as protein- and DNA-recognition, which would allow the design of simple functional systems. This research project aims to use the de novo designed parallel heterodimeric coiled-coil motif as a template in the synthesis of peptide chains and cyclic peptides. The synthesis strategy is based on the association of coil strands, which are linked to the amino acid to be transferred and to the growing peptide chain via a thioester bond. Based on the chemistry of the native chemical ligation, the peptide chain is elongated from the N-to the C-terminus. The thioester linkage allows subsequent head-to-tail cyclization, which is also intended to be mediated by coiled-coil interaction. It is planned to develop a solid-phase and a solution-phase synthesis approach. For the solid-phase synthesis, control of the individual reaction steps is achieved by tuning the reaction-buffer conditions. However, to control the coiled-coil-mediated peptide synthesis in solution, a coiled-coil code using orthogonally interacting coiled coils will be developed. Both synthesis strategies will be applied in the design and assembly of cyclic peptide libraries.The project is based in the research field of synthetic biology which aims to use simple building blocks to mimic complex biological systems.