Directed Denaturation:  Room Temperature and Stoichiometric Unfolding of Cytochrome c by a Metalloporphyrin Dimer

Abstract

Using circular dichroism, UV-vis, and trypsin proteolysis, we have shown how a metalloporphyrin dimer induces the unfolding of a protein, cytochrome c, under physiologically relevant conditions and accelerates its rate of proteolytic degradation.

Metal complexes as “protein surface mimetics”

“…154 A change in the binding with a change from a 1:1 binding to a 2:1 (protein:complex) stoichiometry was observed on increasing the temperature from 25 to 70 °C. This result in particular adds to the original conceptual observation from the Hamilton group, 128 in that it implies negative co-operative binding to the unfolded form of Cyt c is favoured.…”

Recent advances in biosensory and medicinal therapeutic applications of zinc(II) and copper(II) coordination complexes

“…Hamilton and coworkers showed that Cu(II)-porphyrins, which are believed to exist as dimers in aqueous solution, lowered the temperature at which cytochrome c undergoes denaturation (T M ) by ∼50 • C, as determined by UV absorbance and CD [116]. In subsequent work, Hamilton et al characterized polyanionic Cu(II)-porphyrin dimer mediated catalysis of the denaturation-mediated proteolysis of cytochrome c under physiological conditions by natural proteases (19, Fig.…”

Recognition of exterior protein surfaces using artificial ligands based on calixarenes, crown ethers, and tetraphenylporphyrins

“…Because the melting point of cytochrome c in the presence of the tetrabiphenylporphyrinbased receptor is influenced by ionic strength, electrostatic interactions contribute to the complexation. Metalloporphyrin derivatives have also been prepared for complexation with cytochrome c [109], and dimeric Cu(II)-porphyrins were effective for denaturation.…”

“…Complexation with the copper TPP derivatives accelerates denaturation and proteolytic degradation of heme proteins with trypsin [109][110][111]. In the presence of four equivalents of the dimeric Cu(II)-porphyrin, tryptic digestion of cytochrome c was advanced compared with the porphyrin free condition.…”

“…Fluorescence or a lack of fluorescence was observed depending on the complexation between the TPP derivatives and proteins, and each column of the plate corresponded to a unique fingerprint that was characteristic to a specific protein. [109] mainly based on the complementary charges and hydrophobic interaction. For example, the cationic protein cytochrome c is bound by negatively charged fluorophores, whereas the anionic protein ferredoxin is bound by positively charged fluorophores.…”