title: A Pictet-Spengler ligation for protein chemical modification.
abstract: Aldehyde- and ketone-functionalized proteins are appealing substrates for the development of chemically modified biotherapeutics and protein-based materials. Their reactive carbonyl groups are typically conjugated with α-effect nucleophiles, such as substituted hydrazines and alkoxyamines, to generate hydrazones and oximes, respectively. However, the resulting C=N linkages are susceptible to hydrolysis under physiologically relevant conditions, which limits the utility of such conjugates in biological systems. Here we introduce a Pictet-Spengler ligation that is based on the classic Pictet-Spengler reaction of aldehydes and tryptamine nucleophiles. The ligation exploits the bioorthogonal reaction of aldehydes and alkoxyamines to form an intermediate oxyiminium ion; this intermediate undergoes intramolecular C-C bond formation with an indole nucleophile to form an oxacarboline product that is hydrolytically stable. We used the reaction for site-specific chemical modification of glyoxyl- and formylglycine-functionalized proteins, including an aldehyde-tagged variant of the therapeutic monoclonal antibody Herceptin. In conjunction with techniques for site-specific introduction of aldehydes into proteins, the Pictet-Spengler ligation offers a means to generate stable bioconjugates for medical and materials applications.
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720, USA.
authors.forename: Paresh
authors.initials: P
authors.lastname: Agarwal
authors.forename: Joep
authors.initials: J
authors.lastname: van der Weijden
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Sletten
authors.forename: David
authors.initials: D
authors.lastname: Rabuka
authors.forename: Carolyn R
authors.initials: CR
authors.lastname: Bertozzi
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D061067:Antibodies, Monoclonal, Humanized / Q000737:chemistry; D057005:Bioengineering / Q000379:methods*; D001691:Biological Therapy / Q000379:methods*; D007659:Ketones / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011506:Proteins / Q000737:chemistry*; D000068878:Trastuzumab; D014363:Tryptamines / Q000737:chemistry*
chemical_list: D000447:Aldehydes; D061067:Antibodies, Monoclonal, Humanized; D007659:Ketones; D011506:Proteins; D014363:Tryptamines; D000068878:Trastuzumab