A Novel Complex: A Quantum Dot Conjugated to an Active T7 RNA Polymerase

Abstract

To perform single‐molecule studies of the T7 RNA polymerase, it is crucial to visualize an individual T7 RNA polymerase, for example, through a fluorescent signal. We present a novel complex combining two different molecular functions, an active T7 RNA polymerase and a highly luminescent nanoparticle, a quantum dot. The complex has the advantage of both constituents: the complex can traffic along DNA and simultaneously be visualized, both at the ensemble and at the single‐molecule level. The labeling was mediated through an in vivo biotinylation of a His‐tagged T7 RNA polymerase and subsequent binding of a streptavidin‐coated quantum dot. Our technique allows for easy purification of the quantum dot labeled T7 RNA polymerases from the reactants. Also, the conjugation does not alter the functionality of the polymerase; it retains the ability to bind and transcribe.