Identification of Nudix Hydrolase Family Members with an Antimutator Role in Mycobacterium tuberculosis and Mycobacterium smegmatis
http://www.100md.com
《细菌学杂志》
Unite de Genetique Mycobacterienne, Institut Pasteur, Paris, France,Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología (CSIC), Madrid, Spain,INSERM U570, Faculte Necker-Enfants Malades, Universite Rene Descartes, Paris, France
ABSTRACT
Mycobacterium tuberculosis and Mycobacterium smegmatis MutT1, MutT2, MutT3, and Rv3908 (MutT4) enzymes were screened for an antimutator role. Results indicate that both MutT1, in M. tuberculosis and M. smegmatis, and MutT4, in M. smegmatis, have that role. Furthermore, an 8-oxo-guanosine triphosphatase function for MutT1 and MutT2 is suggested.
TEXT
Oxidized guanine (8-oxo-G) is a potent mutagen because of its ambiguous pairing with cytosine and adenine. The Escherichia coli MutT protein specifically hydrolyzes both 8-oxo-deoxyguanosine triphosphate (8-oxo-dGTP) and 8-oxo-guanosine triphosphate (8-oxo-rGTP), preventing their misincorporation in DNA and RNA opposite template A (10, 23, 24, 26). The MutT E. coli protein has an antimutator function, and it was the first enzyme of the MutT/Nudix hydrolase family, characterized by a 23-amino-acid region, to be studied. Nudix hydrolases, are so named because the ones characterized so far all hydrolyze a nucleoside diphosphate linked to some other moiety, X. Besides oxidized guanine, they were shown to degrade other substrates, such as NADH, GDP-mannose, or ADP-ribose (2, 3, 8, 9, 14, 15, 18).
Here we have investigated the role of the putative Nudix hydrolases MutT1, MutT2, MutT3, and Rv3908 (MutT4) of M. tuberculosis (5) and their putative M. smegmatis homologues (sequences were obtained from The Institute for Genomic Research [TIGR] website; www.tigr.org) as antimutators (Fig. 1). Sequence subunit analysis did not suggest that these proteins were members of any of the known subfamilies of Nudix hydrolases (6, 13, 28). The mutT1 M. tuberculosis knockout mutant (MT1K) was isolated from the transposon library described previously (12). Selection was done by plating aliquots of each independent insertional mutant onto 7H10 plates containing rifampin (Rif) at 2 μg/ml, two times the MIC of Rif for M. tuberculosis used by Morlock et al. (17). One of the clones giving a higher number of Rif-resistant (Rifr) colonies than the wild-type strain harbored an insertion in mutT1. All other mutants were generated by allelic replacement using a replication temperature-sensitive vector harboring the counterselectable marker sacB to carry a kanamycin cassette-disrupted copy of the genes of interest (20). The bacterial strains, plasmids, and primers employed in this study are provided in the supplemental material. DNA isolation, cloning, and Southern hybridization were performed according to standard techniques. Complemented strains of the M. smegmatis mutants were generated by electroporation of the pVV16-derived vectors (11) described in the supplemental material. In 20 independent experiments, we carried out an adapted Luria-Delbruck fluctuation test, as described by Morlock et al. (17). The results obtained are summarized in Table 1. MutT1 deficiency in M. tuberculosis resulted in a 15.5-fold spontaneous mutation frequency increase by rifampin resistance screening compared with the wild-type strain. A similar 12-fold increase was observed for the mutT1 mutant of M. smegmatis. Furthermore, we observed a striking 48.1-fold increase in spontaneous Rifr colonies for the MutT4-deficient M. smegmatis strain. By contrast, we observed no increase for the MutT4-deficient M. tuberculosis strain. One may hypothesize the existence of enzymes with functions redundant to that of MutT4 in M. tuberculosis, thus masking the effect of MutT4 deficiency in these species. Defects in mutT2 and mutT3 genes resulted in no apparent differences between mutants and wild type. Moreover, similar results were obtained when screening for isoniazid resistance (data not shown). Complementation of the mutT1 and mutT4 mutants of M. smegmatis with wild-type copies of the M. smegmatis or M. tuberculosis mutT1 and mutT4 genes reduced the mutation frequency to that seen in the wild type (see the supplemental material), indicating that the genes from both sources were capable of restoring wild-type mutation frequencies in the mutants.
In order to investigate the possible function of these mycobacterial MutT proteins, we sequenced the rpoB gene cluster I region of 32 randomly picked Rifr colonies derived from each mutant, as described by Rad et al. (22). The results are shown in Table 1. As described previously for MutT-defective E. coli (10), we observed 95- to 165- and 7- to 32-fold increases in A-to-C transversions for the mutT1- and mutT2-deficient M. tuberculosis and M. smegmatis, respectively, in comparison with the wild type. We found that M. smegmatis MutT3-deficient strains displayed 518-codon deletions and previously undescribed double 508/509-codon deletions (19). MutT4 deficiency in M. smegmatis was associated with a very high number of T-to-C mutations.
To assess the possible function of these proteins, enzyme assays were performed with 8-oxo-dGTP and other known Nudix hydrolase substrates. The strains for production of the recombinant proteins were obtained by transforming the pVV16-derived vectors in M. smegmatis mc2155. Recombinant proteins, which carry a six-histidine tag at the carboxyl terminus, were partially purified using a Ni-nitrilotriacetic acid superflow QIAGEN resin as described by Stadthagen et al. (25). The standard reaction mixture was in 50 μl of a solution containing 50 mM Tris-Cl (pH 8.5), 5 mM Mg2+, 25 mM NaCl, 2 mM substrate, 0.5 U of yeast inorganic pyrophosphatase for substrates such as (deoxy)nucleoside triphosphates and their derivatives (or 4 U of alkaline phosphatase for all other substrates), and the excess 5 μg of the partially purified extracts. The solution was incubated at 37°C for 30 min, and the reaction was stopped by the addition of 250 μl of 4 mM EDTA (or a Norit suspension to remove unreacted triphosphates). The liberated inorganic orthophosphate was assayed by the colorimetric procedure of Fiske and SubbaRow (7) as modified by Ames and Dubin (1). The results, normalized for a control reaction of an M. smegmatis strain carrying the empty vector, are shown in Fig. 2. As suggested by the rpoB sequencing, MutT1 and MutT2 displayed a clear 8-oxo-GTPase activity. Additionally, as reported for human and E. coli MutT, these proteins exhibited hydrolytic activity on dGTP. Although conclusions on the substrate specificities of our enzymes cannot readily be drawn from our experiments, MutT4 seemed to display a greater hydrolytic activity on dATP than on other substrates under the conditions used in our assay. No recombinant MutT3 protein could be obtained in a suitable form for analysis. Because no antimutator phenotype was suggested for this gene, we did not pursue its analysis.
For M. tuberculosis, with the exception of the dnaE2 role in inducible mutagenesis (4), no other gene was found to be associated with a mutator or antimutator phenotype (16). Strains of the M. tuberculosis W-Beijing family were linked with an increased risk of resistance (21). Sequencing studies revealed that W-Beijing strains could be divided into several branches according to the accumulation of unique missense alterations in three putative antimutator genes, including two of the oxidative damage-related mutT type, mutT2 and mutT4 (22). A previous study by Werngren and Hoffner (27) revealed no mutator phenotype for W-Beijing strains. However, those results do not specify which types of W-Beijing strains were used; hence no definite conclusions could yet be made. Here we describe an apparent antimutator role for the MutT1 enzyme of M. tuberculosis and M. smegmatis. Additionally, our results suggest that this enzyme shares with MutT2 the function of E. coli MutT, which is in apparent contrast with the observed antimutator role for MutT1, but not for MutT2, and this may account for the low number of Rifr colonies found for the mutator MutT1-deficient strains, compared with the numbers observed in other bacteria deficient in MutT enzymes. At present, we have no satisfactory explanation for the conflicting data. One may hypothesize that MutT1 has broader substrate specificity than MutT2. This is the first example of a gene with an antimutator role in M. tuberculosis. Besides 8-oxo-dGTPase activity, this gene's complete role is still unknown. Further studies might elucidate its predominance over MutT2.
ACKNOWLEDGMENTS
This work received support from the European Commission (grant QLK2-CT-2000-00630 and VACSIS project ICA4-CT-2002-10052), the GPH-05 of Institut Pasteur, and the Louis D. French Award. J. Blazquez was supported by the grant BFU2004-0079 from the Spanish Ministerio de Educacion y Ciencia.
We thank Mary Jackson and Jana Kurdulakova for help with the manuscript and critical discussions.
REFERENCES
Ames, B. N., and D. T. Dubin. 1960. The role of polyamines in the neutralization of bacteriophage deoxyribonucleic acid. J. Biol. Chem. 235:769-775.
Bessman, M. J., D. N. Fricks, and S. F. O'Handley. 1996. The MutT proteins or "Nudix" hydrolases, a family of versatile, widely distributed, "housecleaning" enzymes. J. Biol. Chem. 41:25059-25062.
Bhatnagar, S. K., L. C. Bullions, and M. J. Bessman. 1991. Characterization of the MutT nucleoside triphosphatase of Escherichia coli. J. Biol. Chem. 266:9050-9054.
Boshoff, H. I., M. B. Reed, C. E. Barry III, and V. Mizrahi. 2003. DnaE2 polymerase contributes to in vivo survival and the emergence of drug resistance in Mycobacterium tuberculosis. Cell 2:183-193.
Cole, S. T., R. Brosch, J. Parkhill, T. Garnier, C. Churcher, D. Harris, S. V. Gordon, K. Eiglmeier, S. Gas, C. E. Barry III, F. Tekaia, K. Badcock, D. Basham, D. Brown, T. Chillingworth, R. Connor, R. Davies, K. Devlin, T. Feltwell, S. Gentles, N. Hamlin, S. Holroyd, T. Hornsby, K. Jagels, A. Krogh, J. McLean, S. Moule, L. Murphy, K. Oliver, J. Osborne, M. A. Quail, M. A. Rajandream, J. Rogers, S. Rutter, K. Seeger, J. Skelton, R. Squares, S. Squares, J. E. Sulston, K. Taylor, S. Whitehead, and B. G. Barrell. 1998. Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence. Nature 6685:537-544.
Dunn, C. A., S. O'Handley, D. N. Frick, and M. J. Bessman. 1999. Studies on the ADP-ribose pyrophosphatase subfamily of the Nudix hydrolases and tentative identification of trgB, a gene associated with tellurite resistance. J. Biol. Chem. 274:32318-32324.
Fiske, C. H., and Y. SubbaRow. 1925. The colorimetric determination of phosphorous. J. Biol. Chem. 66:375-400.
Frick, D. N., and M. J. Bessman. 1995. Cloning, purification, and properties of a novel NADH pyrophosphatase. Evidence for a nucleotide pyrophosphatase catalytic domain in MutT-like enzymes. J. Biol. Chem. 270:1529-1534.
Frick, D. N., B. D. Townsend, and M. J. Bessman. 1995. A novel GDP-mannose mannosyl hydrolase shares homology with the MutT family of enzymes. J. Biol. Chem. 270:24086-24091.
Horst, J. P., T. H. Wu, and M. G. Marinus. 1999. Escherichia coli mutator genes. Trends Microbiol. 7:29-36.
Jackson, M., D. C. Crick, and P. J. Brennan. 2000. Phosphatidylinositol is an essential phospholipid of mycobacteria. J. Biol. Chem. 39:30092-30099.
Jackson, M., C. Raynaud, M. A. Laneelle, C. Guilhot, C. Laurent-Winter, D. Ensergueix, B. Gicquel, and M. Daffe. 1999. Inactivation of the antigen 85C gene profoundly affects the mycolate content and alters the permeability of the Mycobacterium tuberculosis cell envelope. Mol. Microbiol. 31:1573-1587.
Kang, L. W., S. B. Gabelli, M. A. Bianchet, W. L. Xu, M. J. Bessman, and L. M. Amzel. 2003. Structure of a coenzyme A pyrophosphatase from Deinococcus radiodurans: a member of the Nudix family. J. Bacteriol. 185:4110-4118.
Maki, H., and M. Sekiguchi. 1992. MutT protein specifically hydrolyzes a potent mutagenic substrate for DNA synthesis. Nature 355:273-275.
Mildvan, A. S., Z. Xia, H. F. Azurmeni, V. Saraswat, P. M. Legler, M. A. Massiah, S. B. Gabelli, M. A. Bianchet, L.-W. Kang, and L. M. Amzel. 2005. Structures and mechanisms of Nudix hydrolases. Arch. Biochem. Biophys. 433:129-143.
Mizrahi, V., and S. J. Andersen. 1998. DNA repair in Mycobacterium tuberculosis. What have we learnt from the genome sequence Mol. Microbiol. 29:1331-1339.
Morlock, G. P., B. B. Plikaytis, and J. T. Crawford. 2000. Characterization of spontaneous, in vitro-selected, rifampin-resistant mutants of Mycobacterium tuberculosis strain H37Rv. Antimicrob. Agents Chemother. 12:3298-3301.
O'Handley, S. F., D. N. Frick, C. A. Dunn, and M. J. Bessman. 1998. Orf186 represents a new member of the Nudix hydrolases, active on adenosine(5')triphospho(5')adenosine, ADP-ribose, and NADH. J. Biol. Chem. 273:3192-3197.
O'Sullivan, D. M., T. D. McHugh, and S. H. Gillespie. 2005. Analysis of rpoB and pncA mutations in the published literature: an insight into the role of oxidative stress in Mycobacterium tuberculosis evolution J. Antimicrob. Chemother. 5:674-679.
Pelicic, V., M. Jackson, J. M. Reyrat, W. R. Jacobs, Jr., B. Gicquel, and C. Guilhot. 1997. Efficient allelic exchange and transposon mutagenesis in Mycobacterium tuberculosis. Proc. Natl. Acad. Sci. USA 94:10955-10960.
Pfyffer, G. E., A. Strassle, T. van Gorkum, F. Portaels, L. Rigouts, C. Mathieu, F. Mirzoyev, H. Traore, and J. D. van Embden. 2001. Multidrug-resistant tuberculosis in prison inmates, Azerbaijan. Emerg. Infect. Dis. 7:855-861.
Rad, M. E., P. Bifani, C. Martin, K. Kremer, S. Samper, J. Rauzier, B. Kreiswirth, J. Blazquez, M. Jouan, D. Van Soolingen, and B. Gicquel. 2003. Mutations in putative mutator genes of Mycobacterium tuberculosis strains of the W-Beijing family. Emerg. Infect. Dis. 9:838-845.
Riyoko, I., H. Hayakawa, M. Sekiguchi, and T. Ishibashi. 2005. Multiple enzyme activities of Escherichia coli MutT protein for sanitization of DNA and RNA precursor pools. Biochemistry 17:6670-6674.
Sekiguchi, M., and T. Tsuzuki. 2002. Oxidative nucleotide damage: consequences and prevention. Oncogene 21:8895-8904.
Stadthagen, G., J. Kordulakova, R. Griffin, P. Constant, I. Bottova, N. Barilone, B. Gicquel, M. Daffe, and M. Jackson. 2005. p-Hydroxybenzoic acid synthesis in Mycobacterium tuberculosis. J. Biol. Chem. 280:40699-40706.
Taddei, F., H. Hayakawa, M. Bouton, A. Cirinesi, I. Matic, M. Sekiguchi, and M. Radman. 1997. Counteraction by MutT protein of transcriptional errors caused by oxidative damage. Science 278:128-130.
Werngren, J., and S. E. Hoffner. 2003. Drug-susceptible Mycobacterium tuberculosis Beijing genotype does not develop mutation-conferred resistance to rifampin at an elevated rate. J. Clin. Microbiol. 41:1520-1524.
Xu, W., J. Shen, C. A. Dunn, and M. J. Bessman. 2003. A new subfamily of the Nudix hydrolase superfamily active on 5-methyl-UTP (ribo-TTP) and UTP. J. Biol. Chem. 278:37492-37496.(T. Dos Vultos, J. Blazque)
ABSTRACT
Mycobacterium tuberculosis and Mycobacterium smegmatis MutT1, MutT2, MutT3, and Rv3908 (MutT4) enzymes were screened for an antimutator role. Results indicate that both MutT1, in M. tuberculosis and M. smegmatis, and MutT4, in M. smegmatis, have that role. Furthermore, an 8-oxo-guanosine triphosphatase function for MutT1 and MutT2 is suggested.
TEXT
Oxidized guanine (8-oxo-G) is a potent mutagen because of its ambiguous pairing with cytosine and adenine. The Escherichia coli MutT protein specifically hydrolyzes both 8-oxo-deoxyguanosine triphosphate (8-oxo-dGTP) and 8-oxo-guanosine triphosphate (8-oxo-rGTP), preventing their misincorporation in DNA and RNA opposite template A (10, 23, 24, 26). The MutT E. coli protein has an antimutator function, and it was the first enzyme of the MutT/Nudix hydrolase family, characterized by a 23-amino-acid region, to be studied. Nudix hydrolases, are so named because the ones characterized so far all hydrolyze a nucleoside diphosphate linked to some other moiety, X. Besides oxidized guanine, they were shown to degrade other substrates, such as NADH, GDP-mannose, or ADP-ribose (2, 3, 8, 9, 14, 15, 18).
Here we have investigated the role of the putative Nudix hydrolases MutT1, MutT2, MutT3, and Rv3908 (MutT4) of M. tuberculosis (5) and their putative M. smegmatis homologues (sequences were obtained from The Institute for Genomic Research [TIGR] website; www.tigr.org) as antimutators (Fig. 1). Sequence subunit analysis did not suggest that these proteins were members of any of the known subfamilies of Nudix hydrolases (6, 13, 28). The mutT1 M. tuberculosis knockout mutant (MT1K) was isolated from the transposon library described previously (12). Selection was done by plating aliquots of each independent insertional mutant onto 7H10 plates containing rifampin (Rif) at 2 μg/ml, two times the MIC of Rif for M. tuberculosis used by Morlock et al. (17). One of the clones giving a higher number of Rif-resistant (Rifr) colonies than the wild-type strain harbored an insertion in mutT1. All other mutants were generated by allelic replacement using a replication temperature-sensitive vector harboring the counterselectable marker sacB to carry a kanamycin cassette-disrupted copy of the genes of interest (20). The bacterial strains, plasmids, and primers employed in this study are provided in the supplemental material. DNA isolation, cloning, and Southern hybridization were performed according to standard techniques. Complemented strains of the M. smegmatis mutants were generated by electroporation of the pVV16-derived vectors (11) described in the supplemental material. In 20 independent experiments, we carried out an adapted Luria-Delbruck fluctuation test, as described by Morlock et al. (17). The results obtained are summarized in Table 1. MutT1 deficiency in M. tuberculosis resulted in a 15.5-fold spontaneous mutation frequency increase by rifampin resistance screening compared with the wild-type strain. A similar 12-fold increase was observed for the mutT1 mutant of M. smegmatis. Furthermore, we observed a striking 48.1-fold increase in spontaneous Rifr colonies for the MutT4-deficient M. smegmatis strain. By contrast, we observed no increase for the MutT4-deficient M. tuberculosis strain. One may hypothesize the existence of enzymes with functions redundant to that of MutT4 in M. tuberculosis, thus masking the effect of MutT4 deficiency in these species. Defects in mutT2 and mutT3 genes resulted in no apparent differences between mutants and wild type. Moreover, similar results were obtained when screening for isoniazid resistance (data not shown). Complementation of the mutT1 and mutT4 mutants of M. smegmatis with wild-type copies of the M. smegmatis or M. tuberculosis mutT1 and mutT4 genes reduced the mutation frequency to that seen in the wild type (see the supplemental material), indicating that the genes from both sources were capable of restoring wild-type mutation frequencies in the mutants.
In order to investigate the possible function of these mycobacterial MutT proteins, we sequenced the rpoB gene cluster I region of 32 randomly picked Rifr colonies derived from each mutant, as described by Rad et al. (22). The results are shown in Table 1. As described previously for MutT-defective E. coli (10), we observed 95- to 165- and 7- to 32-fold increases in A-to-C transversions for the mutT1- and mutT2-deficient M. tuberculosis and M. smegmatis, respectively, in comparison with the wild type. We found that M. smegmatis MutT3-deficient strains displayed 518-codon deletions and previously undescribed double 508/509-codon deletions (19). MutT4 deficiency in M. smegmatis was associated with a very high number of T-to-C mutations.
To assess the possible function of these proteins, enzyme assays were performed with 8-oxo-dGTP and other known Nudix hydrolase substrates. The strains for production of the recombinant proteins were obtained by transforming the pVV16-derived vectors in M. smegmatis mc2155. Recombinant proteins, which carry a six-histidine tag at the carboxyl terminus, were partially purified using a Ni-nitrilotriacetic acid superflow QIAGEN resin as described by Stadthagen et al. (25). The standard reaction mixture was in 50 μl of a solution containing 50 mM Tris-Cl (pH 8.5), 5 mM Mg2+, 25 mM NaCl, 2 mM substrate, 0.5 U of yeast inorganic pyrophosphatase for substrates such as (deoxy)nucleoside triphosphates and their derivatives (or 4 U of alkaline phosphatase for all other substrates), and the excess 5 μg of the partially purified extracts. The solution was incubated at 37°C for 30 min, and the reaction was stopped by the addition of 250 μl of 4 mM EDTA (or a Norit suspension to remove unreacted triphosphates). The liberated inorganic orthophosphate was assayed by the colorimetric procedure of Fiske and SubbaRow (7) as modified by Ames and Dubin (1). The results, normalized for a control reaction of an M. smegmatis strain carrying the empty vector, are shown in Fig. 2. As suggested by the rpoB sequencing, MutT1 and MutT2 displayed a clear 8-oxo-GTPase activity. Additionally, as reported for human and E. coli MutT, these proteins exhibited hydrolytic activity on dGTP. Although conclusions on the substrate specificities of our enzymes cannot readily be drawn from our experiments, MutT4 seemed to display a greater hydrolytic activity on dATP than on other substrates under the conditions used in our assay. No recombinant MutT3 protein could be obtained in a suitable form for analysis. Because no antimutator phenotype was suggested for this gene, we did not pursue its analysis.
For M. tuberculosis, with the exception of the dnaE2 role in inducible mutagenesis (4), no other gene was found to be associated with a mutator or antimutator phenotype (16). Strains of the M. tuberculosis W-Beijing family were linked with an increased risk of resistance (21). Sequencing studies revealed that W-Beijing strains could be divided into several branches according to the accumulation of unique missense alterations in three putative antimutator genes, including two of the oxidative damage-related mutT type, mutT2 and mutT4 (22). A previous study by Werngren and Hoffner (27) revealed no mutator phenotype for W-Beijing strains. However, those results do not specify which types of W-Beijing strains were used; hence no definite conclusions could yet be made. Here we describe an apparent antimutator role for the MutT1 enzyme of M. tuberculosis and M. smegmatis. Additionally, our results suggest that this enzyme shares with MutT2 the function of E. coli MutT, which is in apparent contrast with the observed antimutator role for MutT1, but not for MutT2, and this may account for the low number of Rifr colonies found for the mutator MutT1-deficient strains, compared with the numbers observed in other bacteria deficient in MutT enzymes. At present, we have no satisfactory explanation for the conflicting data. One may hypothesize that MutT1 has broader substrate specificity than MutT2. This is the first example of a gene with an antimutator role in M. tuberculosis. Besides 8-oxo-dGTPase activity, this gene's complete role is still unknown. Further studies might elucidate its predominance over MutT2.
ACKNOWLEDGMENTS
This work received support from the European Commission (grant QLK2-CT-2000-00630 and VACSIS project ICA4-CT-2002-10052), the GPH-05 of Institut Pasteur, and the Louis D. French Award. J. Blazquez was supported by the grant BFU2004-0079 from the Spanish Ministerio de Educacion y Ciencia.
We thank Mary Jackson and Jana Kurdulakova for help with the manuscript and critical discussions.
REFERENCES
Ames, B. N., and D. T. Dubin. 1960. The role of polyamines in the neutralization of bacteriophage deoxyribonucleic acid. J. Biol. Chem. 235:769-775.
Bessman, M. J., D. N. Fricks, and S. F. O'Handley. 1996. The MutT proteins or "Nudix" hydrolases, a family of versatile, widely distributed, "housecleaning" enzymes. J. Biol. Chem. 41:25059-25062.
Bhatnagar, S. K., L. C. Bullions, and M. J. Bessman. 1991. Characterization of the MutT nucleoside triphosphatase of Escherichia coli. J. Biol. Chem. 266:9050-9054.
Boshoff, H. I., M. B. Reed, C. E. Barry III, and V. Mizrahi. 2003. DnaE2 polymerase contributes to in vivo survival and the emergence of drug resistance in Mycobacterium tuberculosis. Cell 2:183-193.
Cole, S. T., R. Brosch, J. Parkhill, T. Garnier, C. Churcher, D. Harris, S. V. Gordon, K. Eiglmeier, S. Gas, C. E. Barry III, F. Tekaia, K. Badcock, D. Basham, D. Brown, T. Chillingworth, R. Connor, R. Davies, K. Devlin, T. Feltwell, S. Gentles, N. Hamlin, S. Holroyd, T. Hornsby, K. Jagels, A. Krogh, J. McLean, S. Moule, L. Murphy, K. Oliver, J. Osborne, M. A. Quail, M. A. Rajandream, J. Rogers, S. Rutter, K. Seeger, J. Skelton, R. Squares, S. Squares, J. E. Sulston, K. Taylor, S. Whitehead, and B. G. Barrell. 1998. Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence. Nature 6685:537-544.
Dunn, C. A., S. O'Handley, D. N. Frick, and M. J. Bessman. 1999. Studies on the ADP-ribose pyrophosphatase subfamily of the Nudix hydrolases and tentative identification of trgB, a gene associated with tellurite resistance. J. Biol. Chem. 274:32318-32324.
Fiske, C. H., and Y. SubbaRow. 1925. The colorimetric determination of phosphorous. J. Biol. Chem. 66:375-400.
Frick, D. N., and M. J. Bessman. 1995. Cloning, purification, and properties of a novel NADH pyrophosphatase. Evidence for a nucleotide pyrophosphatase catalytic domain in MutT-like enzymes. J. Biol. Chem. 270:1529-1534.
Frick, D. N., B. D. Townsend, and M. J. Bessman. 1995. A novel GDP-mannose mannosyl hydrolase shares homology with the MutT family of enzymes. J. Biol. Chem. 270:24086-24091.
Horst, J. P., T. H. Wu, and M. G. Marinus. 1999. Escherichia coli mutator genes. Trends Microbiol. 7:29-36.
Jackson, M., D. C. Crick, and P. J. Brennan. 2000. Phosphatidylinositol is an essential phospholipid of mycobacteria. J. Biol. Chem. 39:30092-30099.
Jackson, M., C. Raynaud, M. A. Laneelle, C. Guilhot, C. Laurent-Winter, D. Ensergueix, B. Gicquel, and M. Daffe. 1999. Inactivation of the antigen 85C gene profoundly affects the mycolate content and alters the permeability of the Mycobacterium tuberculosis cell envelope. Mol. Microbiol. 31:1573-1587.
Kang, L. W., S. B. Gabelli, M. A. Bianchet, W. L. Xu, M. J. Bessman, and L. M. Amzel. 2003. Structure of a coenzyme A pyrophosphatase from Deinococcus radiodurans: a member of the Nudix family. J. Bacteriol. 185:4110-4118.
Maki, H., and M. Sekiguchi. 1992. MutT protein specifically hydrolyzes a potent mutagenic substrate for DNA synthesis. Nature 355:273-275.
Mildvan, A. S., Z. Xia, H. F. Azurmeni, V. Saraswat, P. M. Legler, M. A. Massiah, S. B. Gabelli, M. A. Bianchet, L.-W. Kang, and L. M. Amzel. 2005. Structures and mechanisms of Nudix hydrolases. Arch. Biochem. Biophys. 433:129-143.
Mizrahi, V., and S. J. Andersen. 1998. DNA repair in Mycobacterium tuberculosis. What have we learnt from the genome sequence Mol. Microbiol. 29:1331-1339.
Morlock, G. P., B. B. Plikaytis, and J. T. Crawford. 2000. Characterization of spontaneous, in vitro-selected, rifampin-resistant mutants of Mycobacterium tuberculosis strain H37Rv. Antimicrob. Agents Chemother. 12:3298-3301.
O'Handley, S. F., D. N. Frick, C. A. Dunn, and M. J. Bessman. 1998. Orf186 represents a new member of the Nudix hydrolases, active on adenosine(5')triphospho(5')adenosine, ADP-ribose, and NADH. J. Biol. Chem. 273:3192-3197.
O'Sullivan, D. M., T. D. McHugh, and S. H. Gillespie. 2005. Analysis of rpoB and pncA mutations in the published literature: an insight into the role of oxidative stress in Mycobacterium tuberculosis evolution J. Antimicrob. Chemother. 5:674-679.
Pelicic, V., M. Jackson, J. M. Reyrat, W. R. Jacobs, Jr., B. Gicquel, and C. Guilhot. 1997. Efficient allelic exchange and transposon mutagenesis in Mycobacterium tuberculosis. Proc. Natl. Acad. Sci. USA 94:10955-10960.
Pfyffer, G. E., A. Strassle, T. van Gorkum, F. Portaels, L. Rigouts, C. Mathieu, F. Mirzoyev, H. Traore, and J. D. van Embden. 2001. Multidrug-resistant tuberculosis in prison inmates, Azerbaijan. Emerg. Infect. Dis. 7:855-861.
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