title: Transglutaminase-mediated N- and C-terminal fluorescein labeling of a protein can support the native activity of the modified protein.
abstract: Fluorescein and its analogs are among the best fluorophores to label proteins and the labeling generally involves chemical modification of a translated protein. Using this methodology, labeling at a specific position remains difficult. It is known that the guinea pig liver transglutaminase (TGase)-catalyzed enzymatic modification method can allow terminal-specific fluorophore labeling of a protein by monodansylcadaverine. However, native activity of the fluorescent protein has not been investigated so far, nor has direct comparison between the chemical modification and the TGase-catalyzed modification been attempted. Therefore, we compared the possibility of fluorescein labeling via chemical labeling and via TGase-catalyzed modification. The latter method was found to be very practical and overcame some of the problems associated with the specificity of the former; fluorescein was covalently attached only to the N- or C-terminal site of glutathione S-transferase when the reaction was catalyzed by TGase and the resulting labeled protein completely retained its native activity. The TGase-mediated labeling occurred not only at room temperature but also at 4 degrees C to the same extent, which is more desirable for preventing the inactivation of proteins.
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Hongo, Tokyo 113-8656, Japan.
authors.forename: Masumi
authors.initials: M
authors.lastname: Taki
authors.forename: Maki
authors.initials: M
authors.lastname: Shiota
authors.forename: Kazunari
authors.initials: K
authors.lastname: Taira
mesh_terms: D001483:Base Sequence; D019793:Fluorescein / Q000737:chemistry* / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005982:Glutathione Transferase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011487:Protein Conformation; D015202:Protein Engineering / Q000379:methods*; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D011503:Transglutaminases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D011503:Transglutaminases; D005982:Glutathione Transferase; D005978:Glutathione; D019793:Fluorescein