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Proc Natl Acad Sci U S A. 1996 Oct 15; 93(21): 11919–11924.

The embAB genes of Mycobacterium avium encode an arabinosyl transferase involved in cell wall arabinan biosynthesis that is the target for the antimycobacterial drug ethambutol.


The antimycobacterial compound ethambutol [Emb; dextro-2,2'-(ethylenediimino)-di-1-butanol] is used to treat tuberculosis as well as disseminated infections caused by Mycobacterium avium. The critical target for Emb lies in the pathway for the biosynthesis of cell wall arabinogalactan, but the molecular mechanisms for drug action and resistance are unknown. The cellular target for Emb was sought using drug resistance, via target overexpression by a plasmid vector, as a selection tool. This strategy led to the cloning of the M. avium emb region which rendered the otherwise susceptible Mycobacterium smegmatis host resistant to Emb. This region contains three complete open reading frames (ORFs), embR, embA, and embB. The translationally coupled embA and embB genes are necessary and sufficient for an Emb-resistant phenotype which depends on gene copy number, and their putative novel membrane proteins are homologous to each other. The predicted protein encoded by embR, which is related to known transcriptional activators from Streptomyces, is expendable for the phenotypic expression of Emb resistance, but an intact divergent promoter region between embR and embAB is required. An Emb-sensitive cell-free assay for arabinan biosynthesis shows that overexpression of embAB is associated with high-level Emb-resistant arabinosyl transferase activity, and that embR appears to modulate the in vitro level of this activity. These data suggest that embAB encode the drug target of Emb, the arabinosyl transferase responsible for the polymerization of arabinose into the arabinan of arabinogalactan, and that overproduction of this Emb-sensitive target leads to Emb resistance.

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  • THOMAS JP, BAUGHN CO, WILKINSON RG, SHEPHERD RG. A new synthetic compound with antituberculous activity in mice: ethambutol (dextro-2,2'-(ethylenediimino)-di-l-butanol). Am Rev Respir Dis. 1961 Jun;83:891–893. [PubMed]
  • Masur H. Recommendations on prophylaxis and therapy for disseminated Mycobacterium avium complex disease in patients infected with the human immunodeficiency virus. Public Health Service Task Force on Prophylaxis and Therapy for Mycobacterium avium Complex. N Engl J Med. 1993 Sep 16;329(12):898–904. [PubMed]
  • Brennan PJ, Nikaido H. The envelope of mycobacteria. Annu Rev Biochem. 1995;64:29–63. [PubMed]
  • Takayama K, Kilburn JO. Inhibition of synthesis of arabinogalactan by ethambutol in Mycobacterium smegmatis. Antimicrob Agents Chemother. 1989 Sep;33(9):1493–1499. [PMC free article] [PubMed]
  • Mikusová K, Slayden RA, Besra GS, Brennan PJ. Biogenesis of the mycobacterial cell wall and the site of action of ethambutol. Antimicrob Agents Chemother. 1995 Nov;39(11):2484–2489. [PMC free article] [PubMed]
  • Wolucka BA, McNeil MR, de Hoffmann E, Chojnacki T, Brennan PJ. Recognition of the lipid intermediate for arabinogalactan/arabinomannan biosynthesis and its relation to the mode of action of ethambutol on mycobacteria. J Biol Chem. 1994 Sep 16;269(37):23328–23335. [PubMed]
  • Snapper SB, Melton RE, Mustafa S, Kieser T, Jacobs WR., Jr Isolation and characterization of efficient plasmid transformation mutants of Mycobacterium smegmatis. Mol Microbiol. 1990 Nov;4(11):1911–1919. [PubMed]
  • Jacobs WR, Barrett JF, Clark-Curtiss JE, Curtiss R., 3rd In vivo repackaging of recombinant cosmid molecules for analyses of Salmonella typhimurium, Streptococcus mutans, and mycobacterial genomic libraries. Infect Immun. 1986 Apr;52(1):101–109. [PMC free article] [PubMed]
  • Belisle JT, Klaczkiewicz K, Brennan PJ, Jacobs WR, Jr, Inamine JM. Rough morphological variants of Mycobacterium avium. Characterization of genomic deletions resulting in the loss of glycopeptidolipid expression. J Biol Chem. 1993 May 15;268(14):10517–10523. [PubMed]
  • Jacobs WR, Jr, Kalpana GV, Cirillo JD, Pascopella L, Snapper SB, Udani RA, Jones W, Barletta RG, Bloom BR. Genetic systems for mycobacteria. Methods Enzymol. 1991;204:537–555. [PubMed]
  • de Bruijn FJ, Lupski JR. The use of transposon Tn5 mutagenesis in the rapid generation of correlated physical and genetic maps of DNA segments cloned into multicopy plasmids--a review. Gene. 1984 Feb;27(2):131–149. [PubMed]
  • Mills JA, McNeil MR, Belisle JT, Jacobs WR, Jr, Brennan PJ. Loci of Mycobacterium avium ser2 gene cluster and their functions. J Bacteriol. 1994 Aug;176(16):4803–4808. [PMC free article] [PubMed]
  • Donnelly-Wu MK, Jacobs WR, Jr, Hatfull GF. Superinfection immunity of mycobacteriophage L5: applications for genetic transformation of mycobacteria. Mol Microbiol. 1993 Feb;7(3):407–417. [PubMed]
  • Lee MH, Pascopella L, Jacobs WR, Jr, Hatfull GF. Site-specific integration of mycobacteriophage L5: integration-proficient vectors for Mycobacterium smegmatis, Mycobacterium tuberculosis, and bacille Calmette-Guérin. Proc Natl Acad Sci U S A. 1991 Apr 15;88(8):3111–3115. [PMC free article] [PubMed]
  • Baulard A, Jourdan C, Mercenier A, Locht C. Rapid mycobacterial plasmid analysis by electroduction between Mycobacterium spp. and Escherichia coli. Nucleic Acids Res. 1992 Aug 11;20(15):4105–4105. [PMC free article] [PubMed]
  • Staden R. The current status and portability of our sequence handling software. Nucleic Acids Res. 1986 Jan 10;14(1):217–231. [PMC free article] [PubMed]
  • Hatfull GF, Sarkis GJ. DNA sequence, structure and gene expression of mycobacteriophage L5: a phage system for mycobacterial genetics. Mol Microbiol. 1993 Feb;7(3):395–405. [PubMed]
  • Smida J, Kazda J, Stackebrandt E. Molecular-genetic evidence for the relationship of Mycobacterium leprae to slow-growing pathogenic mycobacteria. Int J Lepr Other Mycobact Dis. 1988 Sep;56(3):449–454. [PubMed]
  • Narva KE, Feitelson JS. Nucleotide sequence and transcriptional analysis of the redD locus of Streptomyces coelicolor A3(2). J Bacteriol. 1990 Jan;172(1):326–333. [PMC free article] [PubMed]
  • Fernández-Moreno MA, Caballero JL, Hopwood DA, Malpartida F. The act cluster contains regulatory and antibiotic export genes, direct targets for translational control by the bldA tRNA gene of Streptomyces. Cell. 1991 Aug 23;66(4):769–780. [PubMed]
  • Horinouchi S, Kito M, Nishiyama M, Furuya K, Hong SK, Miyake K, Beppu T. Primary structure of AfsR, a global regulatory protein for secondary metabolite formation in Streptomyces coelicolor A3(2). Gene. 1990 Oct 30;95(1):49–56. [PubMed]
  • Stutzman-Engwall KJ, Otten SL, Hutchinson CR. Regulation of secondary metabolism in Streptomyces spp. and overproduction of daunorubicin in Streptomyces peucetius. J Bacteriol. 1992 Jan;174(1):144–154. [PMC free article] [PubMed]
  • Musser JM. Antimicrobial agent resistance in mycobacteria: molecular genetic insights. Clin Microbiol Rev. 1995 Oct;8(4):496–514. [PMC free article] [PubMed]
  • Normark S, Bergström S, Edlund T, Grundström T, Jaurin B, Lindberg FP, Olsson O. Overlapping genes. Annu Rev Genet. 1983;17:499–525. [PubMed]
  • Fernández-Moreno MA, Martínez E, Boto L, Hopwood DA, Malpartida F. Nucleotide sequence and deduced functions of a set of cotranscribed genes of Streptomyces coelicolor A3(2) including the polyketide synthase for the antibiotic actinorhodin. J Biol Chem. 1992 Sep 25;267(27):19278–19290. [PubMed]
  • Sherman DH, Malpartida F, Bibb MJ, Kieser HM, Bibb MJ, Hopwood DA. Structure and deduced function of the granaticin-producing polyketide synthase gene cluster of Streptomyces violaceoruber Tü22. EMBO J. 1989 Sep;8(9):2717–2725. [PMC free article] [PubMed]
  • Donadio S, Staver MJ, McAlpine JB, Swanson SJ, Katz L. Modular organization of genes required for complex polyketide biosynthesis. Science. 1991 May 3;252(5006):675–679. [PubMed]
  • Beck CF, Warren RA. Divergent promoters, a common form of gene organization. Microbiol Rev. 1988 Sep;52(3):318–326. [PMC free article] [PubMed]
  • Miller VL, Taylor RK, Mekalanos JJ. Cholera toxin transcriptional activator toxR is a transmembrane DNA binding protein. Cell. 1987 Jan 30;48(2):271–279. [PubMed]

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