Daniel Grell

Surface grafting onto template-assembled synthetic protein scaffolds in molecular recognition

Creating functional biological molecules de novo requires a detailed understanding of the intimate relationship between primary sequence, folding mechanism, and packing topology, and remains up to now a most challenging goal in protein design and mimicry. As a consequence, the use of well-defined robust macromolecules as scaffolds for the introduction of function by grafting surface residues has become a major objective in protein engineering and de novo design. In this article, the concept of scaffolds is demonstrated on some selected examples, illustrating that novel types of functional molecules can be generated. Reengineered proteins and, most notably, de novo designed peptide scaffolds exhibiting molecular function, are ideal tools for structure-function studies and as leads in drug design.

Targeting molecular recognition: exploring the dual role of functional pseudoprolines in the design of SH3 ligands

Pseudoprolines (ΨPro) have been developed as tools for inducing bioactive conformations that allow for optimal spatial complementation in protein-protein interactions. This dual function of ΨPro was explored for tuning proline-rich peptides as potent ligands for SH3 domains.

Assembly of binding loops on aromatic templates as VCAM-1 mimetics

The design and synthesis of cyclic mimetics of VCAM‐1 protein that reproduce the integrin‐binding domain are presented. The unprotected peptide precursor 37–43, Thr‐Gln‐Ile‐Asp‐Ser‐Pro‐Leu, was grafted onto functional templates of type naphthalene, biphenyl and benzyl through the chemoselective formation of C‐ and N‐terminal oximes resulting in a mixture of four isomeric forms due to syn–anti isomerism of the oxime bonds. Some isomers could be monitored by HPLC and identified by NMR. The molecule containing a naphthalene‐derived template was found to inhibit the VCAM‐1/VLA‐4 interaction more efficiently than previously reported for sulfur‐bridged cyclic peptides containing similar sequences. The finding confirms the importance of incorporating conformational constraints between the terminal ends of the peptide loop 37–43 in the design of synthetic inhibitors of the VCAM‐1/integrin interaction. Copyright

Design and synthesis of a chimeric TASP molecule as potential inhibitor in cell adhesion processes

The construction of protein-like folding motifs as structurally stable scaffolds for the introduction of function represents a major goal in protein design. The use of topol. templates allows the bypass of the well-known folding problem of linear polypeptides and offers a way to mimic native packing topologies by the template directed self-assembly of helical and/or b-sheeted peptide blocks. In conceptually sepg. structure from function, a chimeric 4-helix bundle TASP (Template Assembled Synthetic Protein) derived from the ROP protein and the cell adhesion glycoprotein E-selectin has been designed and synthesized, aimed at inhibiting an early stage in cell adhesion processes, in particular leukocyte adhesion. [on SciFinder (R)]

Pseudoproline libraries for tuning inhibitors of SH3 domain mediated protein-protein interactions

Specific protein-protein interactions are essential facets in cellular communication and the formation and specific assembly of multicomponent protein complexes often is regulated by binding to proline (Pro)-rich peptide sequences. Pro-rich ligands adopt a left-handed polyproline II helical conformation (PPII, all trans amide bonds) and bind to a highly conserved patch of aromatic amino acids of e.g. Src homology (SH3) domains [1]. The essential feature of SH3 binding ligands is the consensus sequence Pro-Xaa-Xaa-Pro (Xaa representing variable amino acids). In the search for novel inhibitors, recently introduced pseudoprolines (ΨPro), i.e. Ser, Thr, Cys derived proline-ring structures with enhanced inherent properties of L-Pro, were used to study ligand receptor interactions of Pro-rich peptides [2]. Binding affinities in the order typically found for SH3-mediated interactions and most notably, enhanced binding specificity as well as inhibition of Grb2 SH3 (N)-SoS complex formation (Figure 1) illustrate that ΨPro building blocks exert a dual functionality, i.e. i) increase and optimization of van der Waals contacts and hydrogen bonding to the receptor molecule, and ii) enhancement of the relevant PPII conformation [3]. To further optimize ligand-receptor interactions in the search of potent SH3 ligands, 2C-substituted ΨPro libraries applying post-insertion strategies have been generated allowing for rapid screening of ligands that optimally complement the SH3 topography.