ABSTRACT
Artificially controlled cell recognition has potentially far-reaching applications in both the understanding and altering of biological function. The event of recognition often involves a multimeric protein binding a cellular membrane. While such an interaction is energetically favorable, it has been surprisingly underexploited in artificial control of recognition. Herein we describe how changing properties of substrate (phosphocholine, PC) self-assembly can affect both binding behavior and substrate affinity to a pentameric recognition protein (C-reactive protein, CRP). PC was modified with a short, self-assembling DNA strand to make the substrate self-assembly sensitive and responsive to ionic environment. A significant shift in CRP binding affinity was observed when substrates were assembled in the presence of Cs(+) rather than K(+). Furthermore, alteration of the linker length tethering PC to DNA showed trends similar to other multivalent systems. In optimizing these linker lengths, positive cooperativity increased and K(d) of the substrate assembly to CRP improved roughly 1000-fold. Such experiments both inform our understanding of biological, multivalent interactions in self-assembling systems and present a potential method to exogenously control events in cell recognition.
Subject(s)
Protein Multimerization , C-Reactive Protein/chemistry , C-Reactive Protein/metabolism , Metals, Alkali/metabolism , Oligodeoxyribonucleotides/metabolism , Phosphorylcholine/metabolism , Protein Binding , Protein Structure, Quaternary , ThermodynamicsABSTRACT
Come together: A novel method for assembling monomers and controlling structure of a de novo helix bundle protein is described. A guanine (G)-rich oligodeoxynucleotide scaffold forms a hydrogen-bonded DNA quadruplex in the presence of potassium counterions, thereby inducing a helical structure and fourfold stoichiometry in conjugated, amphiphilic peptide sequences. The DNA scaffold shows potential for rapidly assembling designed proteins.
Subject(s)
G-Quadruplexes , Oligodeoxyribonucleotides/chemistry , Peptides/chemistry , Amino Acid Sequence , Circular Dichroism , Potassium/chemistry , Protein Folding , Protein Structure, SecondaryABSTRACT
A supramolecular assembly containing an isoguanosine pentaplex with both a "protein-binding" face and a "reporter" face has been generated. When phosphocholine is appended to the protein-binding face this supramolecular assembly binds multivalently to the pentameric human C-reactive protein, a biomolecule implicated in inflammation and heart disease.
