High-affinity labeling and tracking of individual histidine-tagged proteins in live cells using Ni2+ tris-nitrilotriacetic acid quantum dot conjugates.

Investigation of many cellular processes using fluorescent quantum dots (QDs) is hindered by the nontrivial requirements for QD surface functionalization and targeting. To address these challenges, we designed, characterized and applied QD-trisNTA, which integrates tris-nitrilotriacetic acid, a small and high-affinity recognition unit for the ubiquitous polyhistidine protein tag. Using QD-trisNTA, we demonstrate two-color QD tracking of the type-1 interferon receptor subunits in live cells, potentially enabling direct visualization of protein-protein interactions at the single molecule level.

Noncovalent, site-specific biotinylation of histidine-tagged proteins.

Site-specific conjugation of proteins to surfaces, spectroscopic probes, or other functional units is a key task for implementing biochemical assays. The streptavidin-biotin interaction has proven a highly versatile tool for detection, quantification, and functional analysis of proteins. We have developed an approach for site-specific reversible biotinylation of recombinant proteins through their histidine tag using biotin conjugated to the multivalent chelator trisnitrilotriacetic acid (BTtris-NTA).