[ Research Interests ] [ Representative Publications ]

Craig A. Townsend, Ph.D. Professor Department of Chemistry Adjunct Professor Department of Biology Ph.D. Yale University Postdoctoral. Eidgenössiche Technische Hochschule

Department of Chemistry Johns Hopkins University 3400 North Charles Street Baltimore, MD 21218-2685 U.S.A. Office Telephone: Email: 410-516-7444 ctownsend@jhu.edu Office Remsen 252

Research Interests Research programs in Dr. Townsend's group are broadly in bioorganic chemistry with specific interests in natural product biosynthesis, the enzymology and molecular biology of secondary metabolism, small molecule/DNA interactions, and rational drug design. Particular emphasis has been placed on studies of biochemical reaction mechanism and synthesis, notably biomimetic synthesis, discovery of biosynthetic gene clusters and discerning their funcion, mechanistic enzymology and the applications of molecular biology and microbiology in bioorganic chemistry, inhibitor design and synthesis based on understanding of enzyme mechanisms, and the study of and the design and synthesis of sequence-specific DNA cleaving molecules. Major efforts are currently underway with: (1) the aflatoxins, a family of environmental carcinogens of wide distribution and their fundamental engines of synthesis, the polyketide synthases, (2) the b-lactam antibiotics represented classically by penicillin and cephalosporin, but more recently by the nocardicins and their precursor polypeptide synthetases, the potent b-lactamase inhibitor clavulanic acid, and the clinically-important carbapenems, (3) calicheamicin, an exceptionally potent anti-tumor antibiotic of the diynene class with promise as an immunoconjugate drug in Man, and (4) in collaboration with geneticists, microbiologists, pathologists, and oncologists in the Medical School, investigate a cascade of enzymes in Mycobacteria tuberculosis, the causative agent of TB, and closely related proteins highly expressed in human cancer cells, and design and synthesize potential inhibitors/inactivators as potential drugs. Representative Publications Kelly, W. L.; Townsend, C. A. "Protoplast Transformation of the Nocardicin A Producer Nocardia uniformis and Application for Mutational Analysis of nocK and nocL," submitted. Kelly, W. L.; Townsend, C. A. "Mutational Analysis and Characterization of Nocardicin C-9' Epimerase," J. Biol. Chem., 2004, 279, 38220-38227. Gunsior, M.; Ravel, J.; Challis, G. L.; Townsend, C. A. "Engineering p-ydroxyphenylpyruvate Dioxygenase to a p-Hydroxymandelate Synthase and Evidence for the Proposed Benzene Oxide Intermediate in Homogentisate Formation," Biochemistry 2004, 43, 663-674. Gunsior, M.; Breazeale, S. D.; Lind, A. J.; Ravel, J., Janc, J. W.; Townsend, C. A. "The Biosynthetic Gene Cluster for a Monocyclic b-Lactam Antibiotic, Nocardicin A," Chem. & Biol. 2004, to appear July. Stapon, A; Li, R.-F.; Townsend, C. A. "Carbapenem Biosynthesis: Confirmation of Stereochemical Assignments and the Role of CarC in the Ring Stereoinversion Process from L-Proline," J. Amer. Chem. Soc. 2003, 125, 8486-8493. Gerratana, B.; Stapon, A.; Townsend, C. A. "Inhibition and Alternate Substrate Studies on the Mechanism of Carbapenam Synthetase from Erwinia carotovora," Biochemistry 2003, 42, 7836-7847. Miller, M. T.; Gerratana, B.; Stapon, A.; Townsend, C. A.; Rosenzweig, A. C. "Crystal Stucture of Carbapenem Synthetase (CarA)," J. Biol. Chem. 2003, 278, 40996-41002. Zhou, W. B.; Simpson, P. J.; McFadden, J. M.; Townsend, C. A. Medghalchi, S. M.; Vadlamudi, A.; Pinn, M. L.; Ronnett, G. V.; Kuhajda, F. P. "Fatty Acid Synthase Inhibition Triggers Apotosis During S Phase in Human Cells," Cancer Res. 2003, 63, 7330-7337. Stapon, A.; Li, R.-F.; Townsend, C. A. "Synthesis of (3S,5R)-carbapenam-3-carboxylic acid and its role in carbapenem biosynthesis and the stereoinversion problem," J. Amer. Chem. Soc., 2003, 125, 15746-15747. Udwary, D. W.; Casillas, L. K.; Townsend, C. A. "Synthesis of 11-Hydroxyl O-Methylsterigmatocystin and the Role of a Cytochrome P-450 in the Final Step of Aflatoxin Biosynthesis," J. Amer. Chem. Soc. 2002, 124, 5294-5303. Kelly, W. L; Townsend, C. A. "Role of the Cytochrome P450 NocL in Nocardicin A Biosynthesis," J. Amer. Chem. Soc. 2002, 124, 8186-8187. Townsend, C. A. "New Reactions in Clavulanic Acid Biosynthesis," Curr. Opin. Chem. Biol. 2002, 6, 583-589. Watanabe, M. H. C.; Townsend, C. A. "Initial Characterization of a Type I Fatty Acid Synthase and Polyketide Synthase Multienzyme Complex NorS in the Biosynthesis of Aflatoxin B1," Chem. & Biol. 2002, 9, 981-988. Kim, E. K.; Landree, L. E.; Borisy-Rudin, F. F.; Brown, P.; Tihan, T.; Townsend, C. A.; Witters, L. A.; Moran, T. H.; Kuhajda, F. J.; Ronnett, G. V. "Expression of FAS within Hypothalmic Neurons: A Model for Decreased Food Intake After C75 Treatment," Amer. J. Physiol.-Endrocrinol. Metab. 2002, 283, E867-E879. Udwary, D. W.; Merski, M.; Townsend, C. A. "A Method for Prediction of Linker Regions within Large Multifunctional Proteins, and its Application to a Type I Polyketide Synthase," J. Mol. Biol. 2002, 323, 585-598. Miller, M. T.; Bachmann, B. O.; Townsend, C. A.; Rosenzweig, A. C. "The Catalytic Cycle of b-Lactam Synthetase Observed by X-Ray Crystallographic Snapshots," Proc. Nat'l Acad. Sci. 2002, 99, 14752-14757. McFadden, J. M.; Frehywot, G. L.; Townsend, C. A. "A Flexible Route to (5R)-Thiolactomycin, a Naturally-Occurring Inhibitor of Fatty Acid Synthesis," Org. Lett. 2002, 4, 3859-3862. Parrish, N. M.; Houston, T. A.; Jones, P. B.; Townsend, C. A.; Dick, J. D. "In Vitro Activity of a Novel Antimicrobial Compound, N-Octanesulfonylacetamide, and its Effects on Lipid and Mycolic Acid Synthesis," Antimicrob. Agents Chemother. 2001, 45, 1143-1150. Zhou, J.; Kelly, W. L.; Bachmann, B. O.; Gunsior, M.; Townsend, C. A.; Solomon, E. I. "Spectroscopic Studies of Substrate Interactions with Clavaminate Synthase 2, a Multifunctional a-KG-Dependent Non-Heme Iron Enzyme: Correlation with Mechanisms and Reactivities," J. Amer. Chem. Soc. 2001, 123, 7388-7398. Hitchman, T. S.; Schmidt, E. W.; Trail, F.; Rarick, M. D.; Linz, J. E.; Townsend, C. A. "Hexanoate Synthase, a Specialized Type I Fatty Acid Synthase from Aflatoxin B1 Biosynthesis" Bioorg. Chem. 2001, 29, 293-307. Miller, M. T.; Bachmann, B. O.; Townsend, C. A.; Rosenzweig, A. C. "Stucture of b-Lactam Synthetase Reveals How to Synthesize Antibiotics Instead of Asparagine," Nature Struct. Biol. 2001, 8, 684-689. Keller, N. P.; Watanabe, C. M. H.; Kelkar, H. S.; Adams, T. H.; Townsend, C. A. "Requirement of Monooxygenase-Mediated Steps for Sterigmatocystin Biosynthesis by Aspergillus nidulans," Appl. Environ. Microbiol. 2000, 66, 359-362. Challis, G. L.; Ravel, J.; Townsend, C. A. "Predictive, Structure-Based Model of Amino Acid Recognition by Non-Ribosomal Peptide Synthetase Adenylation Domains," Chemistry & Biology 2000, 7, 211-224. Pizer, E. S.; Thupari, J.; Han, W.-F.; Pinn, M. L.; Chrest, F. J.; Frehywot, G. L.; Townsend, C. A.; Kuhajda, F. P. "Malonyl-Coenzyme-A is a Potential Mediator of Cytotoxicity Induced by Fatty Acid Synthase Inhibition in Human Breast Cancer Cells and Xenografts," Cancer Res. 2000, 60, 213-218. Li, R.-F.; Khaleeli, N.; Townsend, C. A. "Expansion of the Clavulanic Acid Gene Cluster: Identification and In vivo Functional Analysis of Three New Genes Required for the Biosynthesis of Clavulanic Acid from Streptomyces clavuligerus," J. Bacteriol. 2000, 182, 4087-4095. Kuhajda, F. P.; Pizer, E. S.; Li J. N.; Mani, N. S.; Frehywot, G. L.; Townsend, C. A. "Synthesis and Anti-tumor Activity of a Novel Inhibitor of Fatty Acid Synthase," Proc. Nat'l Acad. Sci., U.S.A. 2000, 97, 3450-3454. Khaleeli, N.; Busby, R. W.; Townsend, C. A. "Site-Directed Mutagenesis and Biochemical Analysis of the Endogeneous Ligands in the Ferrous Active Site of Clavaminate Synthase. The His-3 Variant of the 2-His-1-Carboxylate Model." Biochemistry 2000, 39, 8666-8673. Loftus, T. M.; Jaworsky D.; Frehywot, G. L.; Townsend, C. A.; Ronnett, G.; Lane, M. D.; Kuhajda, F. J. "Inhibitors of Fatty Acid Synthase Induce Weight Loss: A Link Between Fatty Acid Synthesis and Feeding Behavior," Science 2000, 288, 2379-2381. Bachmann, B. O.; Townsend, C. A. "Kinetic Mechanism of the b-Lactam Synthetase of Streptomyces clavuligerus," Biochemistry 2000, 39, 11187-11193. Jones, P. B.; Parrish, N. M.; Houston, T. A.; Stapon, A. S.; Bansal, N. P.; Dick, J. D.; Townsend, C. A. "A New Class of Anti-Tuberculosis Agents," J. Med. Chem. 2000, 43, 3304-3314. Li. R.-F.; Stapon, A.; Blanchfield, J. T.; Townsend, C. A. "Three Unusual Reactions Mediate Carbapenem and Carbapenam Biosynthesis," J. Amer. Chem. Soc. 2000, 122, 9296-9297. Wu, M.; Stoermer, D.; Townsend, C. A.; Tullius, T. D. "Calicheamicin-Homeodomain Conjugate as an Efficient, Sequence-Specific DNA Cleavage and Mapping Tool," J. Amer. Chem. Soc. 2000, 122, 12884-12885. Iwata-Reuyl, D.; Basak, A.; Townsend, C. A. "b-Secondary Kinetic Isotope Effects in the Clavaminate Synthase-Catalyzed Oxidative Cyclization of Proclavaminic Acid and in Related Azetidinone Model Reactions," J. Amer. Chem. Soc. 1999, 121, 11356-11368. Khaleeli, N.; Li, R.-F.; Townsend, C. A. "Origin of the b-Lactam Carbons in Clavulanic Acid from an Unusual Thiamine Pyrophosphate-Mediated Reaction," J. Amer. Chem. Soc. 1999, 121, 9223-9224. [See 'Perspectives' article: Science 2000, 287, 818-819.] Casillas, L. K.; Townsend, C. A. "Total Synthesis of O-Methylsterigmatocystin Using N-Alkylnitrilium Salts and Carbonyl-Alkene Interconversion in a New Xanthone Synthesis," J. Org. Chem. 1999, 64, 4050-4059. Graybill, T. L.; Casillas, E. G.; Pal, K.; Townsend, C. A. "Silyltriflate-Mediated Ring-Closure and Rearrangement in the Synthesis of Potential Bisfuran-Containing Intermediates of Aflatoxin Biosynthesis," J. Amer. Chem. Soc. 1999, 121, 7729-7746. Pitlik, J., and Townsend, C. A. 1998. Solution-Phase Synthesis of a Combinatorial Monocyclic Beta-Lactam Library: Potential Protease Inhibitors. Bioorg. Med. Chem. Lett. 7, 3129-3134. Watanabe, C. M. H., and Townsend, C. A. 1998. The In Vitro Conversion of Norsolorinic Acid to Aflatoxin B1. An Improved Method of Cell-Free Enzyme Preparation and Stabilization. J. Am. Chem. Soc. 120, In Press. Bachmann, B. O., Li, R., and Townsend, C. A. 1998. "Beta-Lactam Synthetase: A New Class of Biosynthetic Enzyme. Proc. Natl Acad. Sci., U.S.A. 95, accepted. Silva, J. C., and Townsend, C. A. 1997. Heterologous Expression, Isolation and Characterization of Versicolorin B Synthase from Aspergillus parasiticus in Escherichia coli and Saccharomyces cerevisiae. A Key Enzyme in the Aflatoxin B1 Biosynthetic Pathway. J. Biol. Chem. 272, 804-813. Egan, L. A., Busby, R. W., Iwata-Reuyl, D., and Townsend, C. A. 1997. The Probable Role of Clavaminic Acid as the Terminal Intermediate in the Common Pathway to Clavulanic Acid and the Antipodal Clavam Metabolites. J. Am. Chem. Soc. 119, 2348-2355. Mani, N. S., and Townsend, C. A. 1997. A Concise Synthesis of (+)-Cerulenin from a Chiral Oxiranyllithium. J. Org. Chem. 62, 636-640. Minto, R. E., and Townsend, C. A. 1997. Enzymology and Molecular Biology of Aflatoxin Biosynthesis. Chem. Rev. 97, 2537-2555. Townsend, C. A. 1997. Structural Studies of Natural Product Biosynthetic Enzymes. Chem. & Biol. 4, 721-730. Watanabe, C. M. H. and C. A. Townsend., 1996. Incorporation of molecular oxygen in aflatoxin Bl biosynthesis. J. Org. Chem. 61, 1990- 1993. Chatterjee, M., P. J. Smith, and C. A. Townsend. 1996. The role of the aminosugar and helix binding in the thiol-induced activation calicheamicin for DNA cleavage. J. Am. Chem. Soc. 118, 1938-1948. Silva, J. C., Minto, R. E., Barry III, C. E., Holland, K. A.,and Townsend, C. A. 1996. Isolation and Characterization of the Versicolorin B Synthase Gene from Aspergillus parasiticus: Expansion of the Aflatoxin B1 Biosynthetic Gene Cluster. J. Biol. Chem. 271, 13600-13608. McGuire, S. M., Silva, J. C., Casillas, E. G., and Townsend, C. A. 1996. Purification and Characterization of Versicolorin B Synthase from Aspergillus parasiticus. Catalysis of the Stereodifferentiating Cyclization in Aflatoxin Biosynthesis Essential to DNA Interaction. Biochemistry 35, 11470-11486. Watanabe, C. H. M., Wilson, D., Linz, J. E., and Townsend, C. A. 1996. Demonstration of the Catalytic Roles and Evidence for the Physical Association of Type I Fatty Acid Synthases and a Polyketide Synthase in the Biosynthesis of Aflatoxin B1. Chem. & Biol. 3, 463-469. Chatterjee, M., Mah, S. C., Tullius, T. D. and Townsend, C. A. 1995. The Role of the Aryl Iodide in the Sequence-Selective Cleavage of DNA by Calicheamicin. The Importance of Thermodynamic Binding vs. Kinetic Activation in the Cleavage Process. J. Am. Chem. Soc. 117, 8074. Wu, T.-K., Houston, T. A., Busby, R. W., McIlwaine, D. B., Egan, L. A., and Townsend, C. A. 1995. Identification, Cloning, Sequencing and Over Expression of the Gene Encoding Proclavaminate Amidino Hydrolase and Characterization of Protein Function in Clavulanic Acid Biosynthesis. J. Bacteriol. 177, 3714. Busby, R. W., Chang, M. D.-T., Busby, R. C.,Wimp,J.andTownsend,C.A. 1995. Expression and Purification of Two Isozymes of Clavaminate Synthase and Initial Characterization of the Iron Binding Site. General Error Analysis in PCR Amplification. J. Biol. Chem. 270, 4262. J. W., L. A. Egan, and C. A. Townsend 1995. Purification and characterization of clavaminate synthase from Streptomyces antibioticlls: A multifunctional enzyme of clavam biosynthesis. J. Biol. Chem. 270, 5399 5404. T.-K., Houston, T. A., Busby, R. W., McIlwaine, D. B., Egan, L. A., and Townsend, C. A. 1995. Identification, Cloning, Sequencing and Over Expression of the Gene Encoding Proclavaminate Amidino Hydrolase and Characterization of Protein Function in Clavulanic Acid Biosynthesis, J. Bacteriol. 177, 3714-3720. Chatterjee, M., Cramer, K. D., andTownsend, C. A. 1994. Kinetic vs. Thermodynamic Determinants in the Sequence Selectivity of DNA Cleavage by Calicheamicin. J. Am. Chem. Soc. 116, 8819. Chatterjee, M. and Townsend, C. A. 1994. Evidence for the Probable Final Steps in Aflatoxin Biosynthesis. J. Org. Chem. 59, 4424. Brobst, S. W. and Townsend, C. A. 1994. The Potential Role of Fatty Acid Initiation in the Biosynthesis of the Fungal Aromatic Polyketide Aflatoxin B,. Can. J. Chem. 72, 200.

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