Alpha-Helix-Inducing Dimerization of Synthetic Polypeptide Scaffolds on Gold

Abstract

Designed, synthetic polypeptides that assemble into four-helix bundles upon dimerization in solution were studied with respect to folding on planar gold surfaces. A model system with controllable dimerization properties was employed, consisting of negatively and positively charged peptides. Circular dichroism spectroscopy and surface plasmon resonance based measurements showed that at neutral pH, the peptides were able to form heterodimers in solution, but unfavorable electrostatic interactions prevented the formation of homodimers. The dimerization propensity was found to be both pH- and buffer-dependent. A series of infrared absorption-reflection spectroscopy experiments of the polypeptides attached to planar gold surfaces revealed that if the negatively charged peptide was immobilized from a loading solution where it was folded, its structure was retained on the surface provided it had a cysteine residue available for anchoring to gold. If it was immobilized as random coil, it remained unstructured on the surface but was able to fold through heterodimerization if subsequently exposed to a positively charged polypeptide. When the positively charged peptide was immobilized as random coil, heterodimerization could not be induced, probably because of high-affinity interactions between the charged primary amine groups and the gold surface. These observations are intended to pave the way for future engineering of functional surfaces based on polypeptide scaffolds where folding is known to be crucial for function.

A Quantitative, Real‐Time Assessment of Binding of Peptides and Proteins to Gold Surfaces

“…This spreading might be mediated by favorable interactions between positively charged amines on the protein and Au. [30,31] This hypothesis is strengthened by the reversibility of binding of the different peptides applied on their own on Au NPs. Even the best binding peptide, 3 His, dissociated readily, with 1 His dissociating even faster (data not shown).…”

Polypeptide functionalized gold nanoparticles for bioanalytical applications

“…It is also possible to design polypeptides that folds into a helical structure as a result of an interaction with a surface, [62][63] or with a complimentary peptide. 30,64 Alternatively, helices can be formed in response to external stimuli such as change of pH, 36 change of temperature, 65 or the presence of metal cations. [66][67] In this thesis de novo designed polypeptides are utilized in all papers.…”

“…The mixture of these two peptides in a 1:1 stoichiometric relationship leads to heterodimerization and folding with a a The one letter abbreviation for Glu is E. dissociation constant of 20 µM, according to a circular dichroism spectroscopy analysis. 64 The complex formation has been further characterized by ultracentrifugation as well as NMR spectroscopy. 30 The utilization of JR2EC and JR2KC for fiber formation but also to assemble nanoparticles is described in more detail elsewhere.…”

Polypeptide-guided assembly of conducting polymer nanocomposites

“…The two synthetic polypeptides used here, JR2E and JR2K, are 42-residue polypeptides that are de novo designed to fold into a helix-loop-helix motif and heterodimerize into four-helix bundles at neutral pH. [18][19][20][21] At neutral pH, the glutamic acid rich polypeptide JR2E has a net charge of -5 whereas JR2K is 5 rich in lysine residues and has a net charge of +11. Charge repulsion prevents homodimer formation at pH 7 and the peptide exists as random coil monomers when kept separate.…”

“…18, 19 Incorporation of a cysteine residue in the loop region (position 22) yielded the polypeptides JR2EC and 10 JR2KC. The thiol group enabled specific and site directed immobilization of JR2EC on planar gold surfaces, 19 and gold nanoparticles.…”