Abstract: Series 99, Lecture 4

The Harvey Lectures Series 99 (2003—2004)

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Lecture #4: Thursday, February 19, 2004 — Time and Location

Breeding Molecules to Spy on Cells

Roger Y Tsien, PhD

Professor of Pharmacology, Chemistry and Biochemistry
Investigator, Howard Hughes Medical Institute

Howard Hughes Medical Institute, University of California, San Diego

San Diego, California

Genetically encoded tags and indicators are molecular spies that enable us to watch specific gene products and biochemical processes in living cells and organisms. The best known genetically encoded tags are fluorescent proteins from jellyfish and corals, which have been artificially bred to cover the entire visible spectrum, to eliminate multimerization, and to report local signals such as redox potential, ion and neurotransmitter concentrations, kinase/phosphatase activities, and protein-protein interactions. Short tetracysteine motifs are complementary tags, which can be labeled in live cells with membrane-permeant biarsenical dyes. Such labeling occurs with picomolar dissociation constants and represents a spectroscopically versatile, organic synthetic alternative to naturally fluorescent proteins. Unique applications include green vs. red pulse-chase labeling of old vs. new copies of the same protein, and electron-microscopic localization and chromophore-assisted light inactivation of a chosen protein without the problems of antibody penetration. Applications of genetically encoded indicators and tetracysteine tags to a variety of cell biological problems will be discussed, as well as orthogonal extensions such as labeling of oligohistidine motifs and RNA aptamers.