The enediyne antibiotic calicheamicin (CLM) γ1I is a prominent antitumor agent that is targeted to DNA by a novel aryltetrasaccharide comprised of an aromatic unit and four unusual carbohydrates. Herein we report the heterologous expression and the biochemical characterization of the two "internal" glycosyltransferases CalG3 and CalG2 and the structural elucidation of an enediyne glycosyltransferase (CalG3). In conjunction with the previous characterization of the "external" CLM GTs CalG1 and CalG4, this study completes the functional assignment of all four CLM GTs, extends the utility of enediyne GT-catalyzed reaction reversibility, and presents conclusive evidence of a sequential glycosylation pathway in CLM biosynthesis. This work also reveals the common GT-B structural fold can now be extended to include enediyne GTs.
|Number of pages||12|
|Journal||Chemistry and Biology|
|State||Published - Aug 25 2008|
Bibliographical noteFunding Information:
We thank the University of Wisconsin–Madison School of Pharmacy Analytical Facility for analytical support, Philip R. Hamann (Wyeth Research) for providing CLM α 3 I , and Gavin J. Williams for helpful discussion. B.R.G. is a postdoctoral fellow of the American Cancer Society (PF-05-016-01-CDD) and J.S.T is a University of Wisconsin H.I. Romnes Fellow. This research was supported in part by National Institutes of Health Grant CA84374 and National Cooperative Drug Discovery Group Grant U19 CA113297 from the National Cancer Institute. The General Medicine and Cancer Institute Collaborative Access Team (GM/CA-CAT) has been funded in whole or in part with federal funds from the National Cancer Institute (Y1-CO-1020) and the National Institute of General Medical Science (Y1-GM-1104). Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Basic Energy Sciences, Office of Science, under contract W-31-109-ENG-38. The authors report competing interests. J.S.T. is a cofounder of Centrose (Madison, WI).
ASJC Scopus subject areas
- Molecular Medicine
- Molecular Biology
- Drug Discovery
- Clinical Biochemistry