Rational Design, Synthesis, Evaluation, and Crystal Structure of a Potent Inhibitor of Human GAR Tfase: 10-(Trifluoroacetyl)-5,10-dideazaacyclic-5,6,7,8-tetrahydrofolic Acid
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- 作者：Yan Zhang ; Joel Desharnais ; Thomas H. Marsilje ; Chenglong Li ; Michael P. Hedrick ; Lata T. Gooljarsingh ; Ali Tavassoli ; Stephen J. Benkovic ; Arthur J. Olson ; Dale L. Boger ; and Ian A. Wilson
- 刊名：Biochemistry
- 出版年：2003
- 出版时间：May 27, 2003
- 年：2003
- 卷：42
- 期：20
- 页码：6043 - 6056
- 全文大小：937K
- 年卷期：v.42,no.20(May 27, 2003)
- ISSN：1520-4995
文摘
Glycinamide ribonucleotide transformylase (GAR Tfase) has been the target of anti-neoplasticintervention for almost two decades. Here, we use a structure-based approach to design a novel folateanalogue, 10-(trifluoroacetyl)-5,10-dideazaacyclic-5,6,7,8-tetrahydrofolic acid (10-CF3CO-DDACTHF, 1),which specifically inhibits recombinant human GAR Tfase (Ki = 15 nM), but is inactive (Ki > 100 
M)against other folate-dependent enzymes that have been examined. Moreover, compound 1 is a potentinhibitor of tumor cell proliferation (IC50 = 16 nM, CCRF-CEM), which represents a 10-fold improvementover Lometrexol, a GAR Tfase inhibitor that has been in clinical trials. Thus, this folate analogue 1 isamong the most potent and selective inhibitors known toward GAR Tfase. Contributing to its efficaciousactivity, compound 1 is effectively transported into the cell by the reduced folate carrier and intracellularlysequestered by polyglutamation. The crystal structure of human GAR Tfase with folate analogue 1 at1.98 Å resolution represents the first structure of any GAR Tfase to be determined with a cofactor orcofactor analogue without the presence of substrate. The folate-binding loop of residues 141-146, whichis highly flexible in both Escherichia coli and unliganded human GAR Tfase structures, becomes highlyordered upon binding 1 in the folate-binding site. Computational docking of the natural cofactor into thisand other apo or complexed structures provides a rational basis for modeling how the natural cofactor10-formyltetrahydrofolic acid interacts with GAR Tfase, and suggests that this folate analogue-boundconformation represents the best template to date for inhibitor design.
M)against other folate-dependent enzymes that have been examined. Moreover, compound 1 is a potentinhibitor of tumor cell proliferation (IC50 = 16 nM, CCRF-CEM), which represents a 10-fold improvementover Lometrexol, a GAR Tfase inhibitor that has been in clinical trials. Thus, this folate analogue 1 isamong the most potent and selective inhibitors known toward GAR Tfase. Contributing to its efficaciousactivity, compound 1 is effectively transported into the cell by the reduced folate carrier and intracellularlysequestered by polyglutamation. The crystal structure of human GAR Tfase with folate analogue 1 at1.98 Å resolution represents the first structure of any GAR Tfase to be determined with a cofactor orcofactor analogue without the presence of substrate. The folate-binding loop of residues 141-146, whichis highly flexible in both Escherichia coli and unliganded human GAR Tfase structures, becomes highlyordered upon binding 1 in the folate-binding site. Computational docking of the natural cofactor into thisand other apo or complexed structures provides a rational basis for modeling how the natural cofactor10-formyltetrahydrofolic acid interacts with GAR Tfase, and suggests that this folate analogue-boundconformation represents the best template to date for inhibitor design.