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A Rapid and Quantitative Fluorimetric Method for Protein-Targeting Small Molecule Drug Screening

We demonstrate a new drug screening method for determining the binding affinity of small drug molecules to a target protein by forming fluorescent gold ...

Agency for Science, Technology and Research (A*STAR)

The same non-covalent interactions previously found to affect the redox potential (E(m)) of the mononuclear T1 Cu protein azurin (Az) are shown to also fine-tune the E(m) of the dinuclear Cu(A) center in the same Az protein scaffold. The effects of these mutations are in the same direction but with smaller magnitude in the Cu(A) site, due to dissipation of the effects by the dinuclear Cu(A) center.

Redox tuning of two biological copper centers through non-covalent interactions: same trend but different magnitude.

Forkhead box protein 1 (FoxA1) is a member of the forkhead family of winged helix transcription factors that plays pivotal roles in the development and differentiation of multiple organs and in the regulation of estrogen-stimulated genes. Conventional analytical methods-electrophoretic mobility shift assay (EMSA) and fluorescence anisotropy (FA)-as well as a gold nanoparticles (AuNPs)-based assay were used to study DNA binding properties of FoxA1 and ligand interruption of FoxA1-DNA binding. In the AuNPs assay, the distinct ability of protein-DNA complex to protect AuNPs against salt-induced aggregation was exploited to screen sequence selectivity and determine the binding affinity constant based on AuNPs color change and absorbance spectrum shift. Both conventional EMSA and FA and the AuNPs assay suggested that FoxA1 binds to DNA in a core sequence-dependent manner and the flanking sequence also played a role to influence the affinity. The EMSA and AuNPs were found to be more sensitive than FA in differentiation of sequence-dependent affinity. With the addition of a spin filtration step, AuNPs assay has been extended for studying small molecular ligand inhibition of FoxA1-DNA interactions enabling drug screening. The results correlate very well with those obtained using FA.

Studying forkhead box protein A1-DNA interaction and ligand inhibition using gold nanoparticles, electrophoretic mobility shift assay, and fluorescence anisotropy.

High throughput screening of small molecular weight (LMW) ligands for protein and sensitive determination of ligand-induced protein stabilization is an important task in drug discovery and in protein structural and functional genomics studies. In this study, gold nanoparticles (AuNPs) and their aggregation property are used to develop a rapid and less equipment intensive assay for screening the interactions between LMW ligands and transcription factors (TFs) and human serum albumin. The assay is based on the fact that the aggregation/discpersion status of AuNPs is very sensitive to the conformation of surrounding proteins, and when a LMW ligand binds to the proteins, it can enhance proteins' salt and thermal stability, and therefore the protective effect on AuNPs from aggregation. Two TFs, i.e. FoxA1 (Forkhead box A1) and AP-2γ (activating enhancer binding protein 2 gamma), and 14 compounds from an NCI compounds library and human serum albumin (HSA) and three known ligands (ibuprofen, warfarin, and phenytoin) are involved to demonstrate the concept and to prove its generality and robustness. With this AuNP method, two strong LMW binders are identified for FoxA1 and AP-2γ; ligand induced protein stabilization is determined. The results have been verified using surface plasmon resonance spectroscopy (SPR) and differential static light scattering (DSLS) techniques. Tryptophan fluorescent measurement is also conducted to provide further information on protein conformational change upon LMW ligand loading as can be observed from AuNPs' UV-vis spectra. FoxA1 and AP-2γ are pivotal in regulating the transcriptional activity of estrogen receptor alpha and controlling the expression of estrogen-responsive breast cancer cells. Identification of drug candidates targeting these two transcription factors could be an alternative in treating breast cancer, in particular those that have become endocrine resistance.

Fast screening of ligand-protein interactions based on ligand-induced protein stabilization of gold nanoparticles.

A facile drug screening method based on synthesis of fluorescent gold nanoclusters inside albumin proteins loaded with small molecular drugs and comparing the relative fluorescence intensities of the resultant gold nanoclusters has been developed and successfully applied for the quantitative measurement of drug-protein binding constants.

Siu Yee New

Institute of Materials Research and Engineering

Agency for Science, Technology and Research (A*STAR)

A Rapid and Quantitative Fluorimetric Method for Protein-Targeting Small Molecule Drug Screening

Siu Yee New

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Institute of Materials Research and Engineering

Agency for Science, Technology and Research (A*STAR)

A Rapid and Quantitative Fluorimetric Method for Protein-Targeting Small Molecule Drug Screening

Institute of Materials Research and Engineering