Site-specific orthogonal labeling of the carboxy terminus of α-tubulin

Abhijit Banerjee, Timothy D. Panosian, Kamalika Mukherjee, Rudravajhala Ravindra, Susannah Gal, Dan L. Sackett, Susan Bane

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


A fluorescent probe has been attached to the carboxy terminus of the α-subunit of α,β-tubulin by an enzymatic reaction followed by a chemical reaction. The unnatural amino acid 3-formyltyrosine is attached to the carboxy terminus of α-tubulin through the use of the enzyme tubulin tyrosine ligase. The aromatic aldehyde of the unnatural amino acid serves as an orthogonal electrophile that specifically reacts with a fluorophore containing an aromatic hydrazine functional group, which in this case is 7-hydrazino-4-methyl coumarin. Conditions for covalent bond formation between the unnatural amino acid and the fluorophore are mild, allowing fluorescently labeled tubulin to retain its ability to assemble into microtubules. A key feature of the labeling reaction is that it produces a red shift in the fluorophore's absorption and emission maxima, accompanied by an increase in its quantum yield; thus, fluorescently labeled protein can be observed in the presence of unreacted fluorophore. Both the enzymatic and coupling reaction can occur in living cells. The approach presented here should be applicable to a wide variety of in vitro systems.

Original languageEnglish (US)
Pages (from-to)777-785
Number of pages9
JournalACS chemical biology
Issue number8
StatePublished - Aug 20 2010

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Medicine


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