个人简介
Education: Undergraduate Degree
BS, 1999, Louisiana State University
Education: Doctoral Degree
Ph.D., 2005, Texas A&M University
Education: Other
Postdoctoral Fellow 2005-2009, Albert Einstein College of Medicine
研究领域
Work in the Frantom group is focused on the field of mechanistic enzymology. In broad terms, mechanistic enzymologists seek a chemical understanding of how enzymes are able to dramatically increase reaction rates, perform unique and stereospecific chemistry, and provide mechanisms for regulation using a limited toolbox consisting of 20 amino acids and various cofactors. In order to answer these types of questions, we utilize a wide array of genetic, biochemical, bioinformatics, biophysical, kinetic, and spectroscopic techniques. Current projects include the following:
1. Investigating Mechanisms of Regulatory and Functional Diversity in an Enzyme Superfamily (funded by NSF CAREER Award MCB-1254077)
As a long-term research goal, the Frantom laboratory looks to understand how allosteric and catalytic mechanisms evolve and work together in multi-domain enzymes. Advances in understanding the dynamic nature of enzymes have identified networks of amino acids involved in inter-domain communication in allosteric systems failing to exhibit large structural changes upon effector binding. However, the underlying mechanisms are not well understood at the molecular level. This lack of understanding creates a major stumbling block for the manipulation of allosterically regulated enzymes, such as engineered biosensors, through modular design methods. Our approach to this problem utilizes “genomic enzymology” where mechanistic enzymology, used to identify mechanisms of catalysis and regulation, is integrated with cutting-edge bioinformatics techniques to identify patterns of evolution within an enzyme superfamily. The DRE-TIM metallolyase superfamily serves as a model system for this project due to its diversity of functions involving the making and breaking of C-C bonds and the allosterically regulated subgroup of Claisen-condensation-like enzymes including α-isopropylmalate synthase (IPMS) and citramalate synthase (CMS). Recent work has focused on comparing mechanisms of allostery and substrate selectivity in evolutionarily distinct IPMS and CMS enzymes. Future projects include functional annotation of enzymes of unknown function in the DRE-TIM metallolyase superfamily, identifying mechanisms of functional evolution between subgroups of the superfamily, and using directed evolution approaches to engineer enzymes with novel C-C bond making and breaking abilities.
2. Investigating Mechanisms of Functional and Catalytic Diversity in Glycosyltransferases
The target of this project is a large class of enzymes called glycosyltransferases (GT). This class of enzymes catalyzes the transferof a sugar molecule (such as glucose) from a nucleotide donor (NDP) to either oxygen or nitrogen atoms in various acceptor molecules including proteins, nucleic acids, lipids, and small molecules. This reaction is involved in many cellular processes such as bacterial cell wall biosynthesis and the cell’s ability to sense its environment. Despite the variety of acceptor molecules, the 3D structures of all GT enzymes to date (nearly 800 individual structures) fall into one of two structures, termed GT-A and GT-B. The GT-A motif is characterized by two independent globular domains in compact association. In contrast, the GT-B motif is more extended and composed of two domains connected by a small linker region. The chemical reaction takes place at the interface of the two domains in both structures. As the two structures are strongly conserved despite the diversity of substrates, we hypothesize that there are regions of the structure critical to function in this class of enzymes. This project integrates biochemical, structural, and bioinformatics approaches to identify structure/function relationships in this enzyme class. Recently, in conjunction with the Busenlehner laboratory, we utilized backbone amide hydrogen/deuterium exchange to identify regions of both GT-A and GT-B enzymes that undergo changes in flexibility upon substrate binding. In the future we will apply bioinformatics and biochemical approaches to investigate if areas with differences in flexibility are evolutionarily conserved and determine their contribution to catalysis. Results from these studies may support the development of novel inhibitors against this important class of enzymes.
近期论文
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Biochemical characterization of the retaining glycosyltransferase glucosyl-3-phosphoglycerate synthase from Mycobacterium tuberculosis Kumar G, Guan S, Frantom PA Arch Biochem Biophys. 2014 Dec 15;564:120-7. doi: 10.1016/j.abb.2014.10.002. Epub 2014 Oct 12 PMID: 25317963
An evolutionarily conserved alternate metal ligand is important for activity in α-isopropylmalate synthase from Mycobacterium tuberculosis Frantom PA, Birman Y, Hays BN, Casey AK Biochim Biophys Acta. 2014 Oct;1844(10):1784-9. doi: 10.1016/j.bbapap.2014.07.013. Epub 2014 Jul 23 PMID: 25064783
Evolutionarily distinct versions of the multidomain enzyme α-isopropylmalate synthase share discrete mechanisms of V-type allosteric regulation Kumar G, Frantom PA Biochemistry. 2014 Jul 29;53(29):4847-56. doi: 10.1021/bi500702u. Epub 2014 Jul 15 PMID: 24991690
Mechanistic and bioinformatic investigation of a conserved active site helix in α-isopropylmalate synthase from Mycobacterium tuberculosis, a member of the DRE-TIM metallolyase superfamily Casey AK, Hicks MA, Johnson JL, Babbitt PC, Frantom PA Biochemistry. 2014 May 13;53(18):2915-25. doi: 10.1021/bi500246z. Epub 2014 Apr 22 PMID: 24720347
V-type allosteric inhibition is described by a shift in the rate-determining step for α-isopropylmalate synthase from Mycobacterium tuberculosis Casey AK, Schwalm EL, Hays BN, Frantom PA Biochemistry. 2013 Oct 1;52(39):6737-9. doi: 10.1021/bi401186v. Epub 2013 Sep 18 PMID: 24033269
The slow-onset nature of allosteric inhibition in α-isopropylmalate synthase from Mycobacterium tuberculosis is mediated by a flexible loop Casey AK, Baugh J, Frantom PA Biochemistry. 2012 Jun 19;51(24):4773-5. doi: 10.1021/bi300671u. Epub 2012 Jun 5 PMID: 22662746
Structural and functional characterization of α-isopropylmalate synthase and citramalate synthase, members of the LeuA dimer superfamily Frantom PA Arch Biochem Biophys. 2012 Mar 15;519(2):202-9. doi: 10.1016/j.abb.2011.10.009. Epub 2011 Oct 19. Review PMID: 22033339
UDP-(5F)-GlcNAc acts as a slow-binding inhibitor of MshA, a retaining glycosyltransferase Frantom PA, Coward JK, Blanchard JS J Am Chem Soc. 2010 May 19;132(19):6626-7. doi: 10.1021/ja101231a PMID: 20411981 Free PMC Article
Chemoenzymatic synthesis of GDP-L-fucose and the Lewis X glycan derivatives Wang W, Hu T, Frantom PA, Zheng T, Gerwe B, Del Amo DS, Garret S, Seidel RD 3rd, Wu P Proc Natl Acad Sci U S A. 2009 Sep 22;106(38):16096-101. doi: 10.1073/pnas.0908248106. Epub 2009 Sep 4 PMID: 19805264 Free PMC Article
Structures and mechanisms of the mycothiol biosynthetic enzymes Fan F, Vetting MW, Frantom PA, Blanchard JS Curr Opin Chem Biol. 2009 Oct;13(4):451-9. doi: 10.1016/j.cbpa.2009.07.018. Epub 2009 Aug 19. Review PMID: 19699138 Free PMC Article
Mapping of the allosteric network in the regulation of alpha-isopropylmalate synthase from Mycobacterium tuberculosis by the feedback inhibitor L-leucine: solution-phase H/D exchange monitored by FT-ICR mass spectrometry Frantom PA, Zhang HM, Emmett MR, Marshall AG, Blanchard JS Biochemistry. 2009 Aug 11;48(31):7457-64. doi: 10.1021/bi900851q PMID: 19606873
Kinetic evidence for interdomain communication in the allosteric regulation of alpha-isopropylmalate synthase from Mycobacterium tuberculosis de Carvalho LP, Frantom PA, Argyrou A, Blanchard JS Biochemistry. 2009 Mar 10;48(9):1996-2004. doi: 10.1021/bi801707t PMID: 19166329 Free PMC Article
Structural and enzymatic analysis of MshA from Corynebacterium glutamicum: substrate-assisted catalysis Vetting MW, Frantom PA, Blanchard JS J Biol Chem. 2008 Jun 6;283(23):15834-44. doi: 10.1074/jbc.M801017200. Epub 2008 Apr 4 PMID: 18390549 Free PMC Article
Direct spectroscopic evidence for a high-spin Fe(IV) intermediate in tyrosine hydroxylase Eser BE, Barr EW, Frantom PA, Saleh L, Bollinger JM Jr, Krebs C, Fitzpatrick PF J Am Chem Soc. 2007 Sep 19;129(37):11334-5. Epub 2007 Aug 23. No abstract available PMID: 17715926 Free PMC Article
Reduction and oxidation of the active site iron in tyrosine hydroxylase: kinetics and specificity Frantom PA, Seravalli J, Ragsdale SW, Fitzpatrick PF Biochemistry. 2006 Feb 21;45(7):2372-9. Erratum in: Biochemistry. 2006 Apr 4;45(13):4338 PMID: 16475826 Free PMC Article
Uncoupled forms of tyrosine hydroxylase unmask kinetic isotope effects on chemical steps Frantom PA, Fitzpatrick PF J Am Chem Soc. 2003 Dec 31;125(52):16190-1 PMID: 14692751 Free PMC Article
Intrinsic deuterium isotope effects on benzylic hydroxylation by tyrosine hydroxylase Frantom PA, Pongdee R, Sulikowski GA, Fitzpatrick PF J Am Chem Soc. 2002 Apr 24;124(16):4202-3 PMID: 11960436
Mutations at four active site residues of biotin carboxylase abolish substrate-induced synergism by biotin Blanchard CZ, Lee YM, Frantom PA, Waldrop GL Biochemistry. 1999 Mar 16;38(11):3393-400 PMID: 10079084
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