Ni-NTA-gold clusters target his-tagged proteins

Addition of six histidines to recombinant proteins has proved useful in the ir purification by nickel-affinity columns. This technology was adapted by synthesizing the chelator for nickel (nitrilotriacetic acid, NTA) onto the surface of gold clusters. These Ni-NTA-gold clusters were shown to specific ally target the 6His region of tagged proteins. Results were verified by co lumn chromatography, dot and overlay blots, UV-Vis spectroscopy, and scanni ng transmission electron microscopy. A 6His-tagged adenovirus "knob" protei n was also shown to maintain receptor binding activity after gold labeling. Two types of gold clusters were used: 1.4-nm Nanogold and a new 1.8-nm "Pe ptideGold" coated with an NTA-dipeptide-thiol. These novel labels should be useful in site-specific high-resolution EM labeling, as well as in metallo graphic development, detection in the light microscope, or direct visualiza tion. (C) 1999 Academic Press.