Chemistry

Golden Proteins

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Science  30 Mar 2012:
Vol. 335, Issue 6076, pp. 1546
DOI: 10.1126/science.335.6076.1546-b

Gold nanoparticles (Au NPs) have long been used as an aid in biological imaging, in part because of their low chemical reactivity. Malay et al. studied the effect of covalent attachment of Au NPs to TRAP (trp RNA-binding attenuation protein), which plays a feedback role in tryptophan biosynthesis in Bacillus, by mutating a Lys residue to Cys. The TRAP protein normally forms a ring of 11 monomers and has been of interest for the delivery of nanoscale objects. However, the incubation of the Cys-bearing protein with 1.4-nm Au NPs created two types of structures similar to viral capsids: hollow shells either 15 to 16 or 21 to 22 nm in diameter. These structures did not form when the native protein was simply mixed with Au NPs, and their formation depended on pH conditions and the concentration of Au NPs. Cryoelectron microscopy also revealed that not all of the capsids retained the Au NPs, which suggests that their role may be to catalyze the rearrangement from the toroidal structure.

Nano Lett. 10.1021/nl3002155 (2012).

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