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JoAnne Stubbe, Ph.D.

Department of Chemistry
Novartis Professor of Chemistry
Professor of Biology

Room 18-598
617-253-1814 (phone)

Biosketch

Ph.D. Chemistry, 1971
University of California, Berkeley

Research Summary

Our general research interests include: (1) Mechanism of natural product DNA Cleavers used clinically 2D NMR methods to determine the structures of the drugs bound to DNA, synthesis and structure of the deoxyribose lesions generated by the drugs and mechanism of repair of these lesions; (2) Mechanism and Regulation of Ribonucleotide Reductases study of clinically active compounds that inactivate reductases; Mechanism of metallo-cofactor assembly in vivo; mechanism of radical initiation using technology to insert unnatural amino acids into the proteins; signal transduction cascades induced by DNA damaging agents; (3) Polyester Biosynthesis understanding non-template driven polymerization reactions and use of bioengineering methods to generate new biodegradable polymers; (4) Mechanism, Structure, and Regulation of the Purine Biosynthetic Pathway studies to understand the importance of transient protein-protein interactions in vivo.

Ribonucleotide Reductases (RNRs)
RNRs are enzymes that catalyze an essensial step in DNA replication and repair. They use unusual metallo-cofactors (a diferric tyrosyl radical, adenosylcobalamin and a glycyl radical). These cofactors serve as radical initiators to generate a cysteinyl radical that initiates radical dependent nucleotide reduction at homologous active sites. Studies are ongoing to understand: the biosynthetic pathway for diferric-tyrosyl radical cofactor assembly in vivo in yeast; the mechanism of radical initiation over 35 using unnatural amino acids and the regulation of dNTP production at all levels. Collaborative efforts with the Griffin, Nocera and Drennan labs are ongoing.

Mechanism of Action of Antitumor Natural Products Metallo-bleomycins (BLMs), are natural products used clinically and act catalytically to destroy DNA. Physical organic methods have been used to understand the chemistry of DNA cleavage. Multidimensional NMR methods using colbalt-BLM and oligonucleotides have been used to elucidate the basis for the chemical and sequence specificity of DNA cleavage. These studies have resulted in a proposal for how one BLM can catalyze ds-DNA cleavage without dissociation from the DNA. NMR methods are being used to investigate the structure of the lesions produced in the DNA backbone by BLM, enedynes, and ionizing radiation. These lesioned DNAs are being used as substrates to understand the mechanism of DNA repair. The genes for the biosynthetic pathways for these natural products have been identified and the glycosylation mechanism are being examined.

Enzymes Involved in Purine Biosynthesis
Understanding the regulation of the purine biosynthetic pathway and the importance of transient protein-protein interactions in the channeling of chemically reactive intermediates produced in this pathway. Our investigations have led to isolation and structural determination of all the enzymes in the pathway giving new insight into the evolution of a biosynthetic pathway. These studies have uncovered a new substrate and two new enzymes in this pathway.

Polyhydroxybutyrate Polymerase (PHB)
The potential for using biological systems as a source of biodegradable thermoplastics is becoming increasingly attractive given the problems associated with oil-based polymers. In collaboration with the Sinskey lab in Biology, studies on the polyhydroxybutyrate polymerases, depolymerases, transcription factors and phasin proteins that govern PHB homeostasis are in progress. The mechanism of homopolymerization reactions is being used to make novel block co-polymers.

Selected Publications

  • Kinetic Studies of PHB Granule Formation by W. eutropha by Transmission Electron Microscopy. J. Tian, A. J. Sinskey and J. Stubbe J. Bacteriol., 187, 3814-3824 (2005).
  • Analysis of Transient PHB Production in W. eutropha H16 by Quantitative Westerns and Transmission Electron Microscopy. J. Tian, A. He, A. Lawrence, P. Liu, N. Watson, A. J. Sinskey and J. Stubbe, J. Bacteriology, 187, 3825-32 (2005).
  • High-frequency 180 Ghz PELDOR. V. P. Denysenkov, T. F. Prisner, J. Stubbe and M. Bennati, Appl. Mag. Res. 29, 1 (2005).
  • Class III Polyhydroxybutyrate Synthase: Involvement in Chain Termination and Re-initiation. J. Tian, A. J. Sinskey and J. Stubbe Biochemistry, 44, 8369-77 (2005).
  • The Active Form of the Saccharomyces cerevisiae Ribonucleotide Reductase Small Subunit is a Heterodimer in Vitro and in Vivo. D. L. Perlstein, J. Ge, A. D. Ortigosa, J. H. Robblee, Z. Zhang, M. Huang and J. Stubbe, Biochemistry, 44, 15366-15377 (2005).
  • EPR Distance Measurements Support a Model for Long-range Radical Initiation in E. coli Ribonucleotide Reductase. M. Bennati, J. H. Robblee, V. Mugnaini, J. Stubbe, J. H. Freed and P. Borbat. J. Am. Chem. Soc. 127, 15014-15015 (2005).

Last Updated: April 16, 2008