An Arsenic Fluorescent Compound as a Novel Probe to Study Arsenic-Binding Proteins

Histidine tag modified magnetic beads for analysis of arsenic binding proteins

BACKGROUND

Many proteins with thiol groups can bind with trivalent arsenic which are termed as arsenic binding proteins, thus change their physiological functions. Therefore, it is vital to analyze the arsenic binding proteins in cells. The Pull-Down strategy based on biotinylated phenylarsenic acid (Bio-PAO(III)) probes is an effective way for analysis of arsenic binding proteins. In this strategy, streptavidin magnetic beads (SA-MBs) was applied to capture the arsenic binding proteins conjugating with Bio-PAO(III) probe. However, strong interaction between SA and biotin makes the elution of arsenic binding proteins not easy.

RESULTS

We developed a novel affinity separation strategy to address the challenge of eluting arsenic binding proteins, a key issue with the existing Bio-PAO(III) Pull-Down method. By employing magnetic beads modified with Nα-Bis(carboxymethyl)-l-lysine (NTA-Lys), polyhistidine-tag (His6-Tag), and SA (MB-NTA(Ni)-His6-SA), we established a more efficient purification process. This innovative approach enables selective capture of arsenic binding proteins in HepG2 cells labeled by Bio-PAO(III) probes, facilitating gentle digestion by trypsin for precise identification through capillary high performance liquid chromatography (Cap HPLC)-electrospray ionization (ESI)-tandem mass spectrometry (MS/MS). What is more, the magnetic beads can be regenerated by using imidazole as the eluent, and the obtained MB-NTA(Ni) can be reloaded with His6-SA for next use. Our method successfully identified 41 arsenic binding proteins, including those involved in cytoskeletal structure, heat shock response, transcriptional regulation, DNA damage repair, redox state regulation, mitochondrial dehydrogenase function, and protein synthesis and structure.

SIGNIFICANCE

This work contributes to a more comprehensive understanding of the toxic mechanisms of arsenic, potentially providing valuable insights for the prevention or treatment of arsenic-related diseases.

Recognition of Proteins by Metal Chelation-Based Fluorescent Probes in Cells

Fluorescent probes such as thiol-reactive and Ni2+-nitrilotriacetate (NTA) based probes provide a powerful toolbox for real-time visualization of a protein and a proteome in living cells. Herein, we first went through basic principles and applications of thiol-reactive based probes in protein imaging and recognition. We then summarize a family of metal-NTA based fluorescence probes in the visualization of His6-tagged protein and identification of metalloproteins at proteome-wide scale. The pros and cons of the probes, as well as ways to optimize them, are discussed.

Therapeutic and analytical applications of arsenic binding to proteins

Knowledge of arsenic binding to proteins advances the development of bioanalytical techniques and therapeutic drugs.