Biochemistry. 1995 Jan 10;34(1):22-31.
Proximity mapping of the Tet repressor-tetracycline-Fe2+ complex by hydrogen peroxide mediated protein cleavage.

Ettner N, Metzger JW, Lederer T, Hulmes JD, Kisker C, Hinrichs W, Ellestad GA, Hillen W.

Lehrstuhl fur Mikrobiologie, Friedrich-Alexander Universitat Erlangen-Nurnberg, FRG.

We demonstrate in a quantitative in vitro induction assay that tetracycline-Fe2+ is a more than 1000-fold stronger inducer of Tet repressor compared to tetracycline-Mg2+. Oxidative cleavage of the Tet repressor-tetracycline-Fe2+ complex with H2O2 and ascorbate results in an Fe(2+)-dependent specific fragmentation of the protein. The maximal yield of about 15% and a reaction time of less than 30 s are only observed in the presence of the drug, whereas about 1% cleavage is obtained after 30 min in the presence of Fe2+ without tetracycline. Cleavage is not inhibited by several radical scavengers, suggesting a highly localized reactivity of the redox-active oxo intermediates in the proximity of the Fe(2+)-tc chelater where they are generated. The products can be separated by HPLC only after denaturation, indicating that the complex is not disrupted by cleavage. Residues at which the cleavage takes place are identified using the masses of the fragments determined by electrospray mass spectrometry and their N-terminal sequences. The major cleavage site maps to residues 104 and 105 of Tet repressor. Less efficient cleavages occur at residues 56 and 136, and the least efficiently cleaved sites are around residues 144 and 147. The cleavage efficiencies correlate to the distances and orientations of the respective peptide bonds to Mg2+ in the crystal structure of the Tet repressor-tetracycline-Mg2+ complex. We discuss potential reaction mechanisms leading to protein cleavage.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7819199&dopt=Abstract antibiotics, tetracycline




Antibiot Khimioter. 1994 Jul;39(7):10-4.
[A new look at the mechanism of action of antibiotics of the tetracycline series. Tetracyclines as components of radical-generating systems]

[Article in Russian]

Petrenko IuM.

Tetracyclines were shown to be able to form radical-generating systems and to affect biological structures at the account of the radical form generation. The radical-generating systems were found to be based on the phenomenon revealed in this study that the tetracyclines catalyzed oxidation of ferrous oxide by oxygen after its binding by these compounds. In the presence of ascorbate the radical formation with the involvement of oxygen could be continuous and accompanied by reduction of ferrous oxide by ascorbate in complex with tetracyclines and its subsequent oxidation as well induced by them. Ca2+ and Mg2+ forming complexes with tetracyclines had no impact on the radical formation. In complex with tetracyclines the ions did not interfere with the tetracycline ability to catalyze oxidation of ferrous oxide after its binding by these compounds. A notion of two functional centres characteristic of tetracyclines was formulated. One of them (chelating) provided the tetracycline binding to Mg2+ and Ca2+ e.g. in ribosomes and the other (toxic) affected the surrounding biological structures by the radical formation.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7840702&dopt=Abstract antibiotics, tetracycline




J Bacteriol. 1983 Aug;155(2):557-64.
Mutations in multicopy Tn10 tet plasmids that confer resistance to inhibitory effects of inducers of tet gene expression.

Moyed HS, Bertrand KP.

Escherichia coli K-12 strains that carry the Tn10 tetracycline resistance determinant (tet) on multicopy plasmids are hypersensitive to 5a,6-anhydrotetracycline and heated chlortetracycline, two tetracycline derivatives that are relatively more effective as inducers of tet gene expression than as inhibitors of bacterial growth. Twenty spontaneous mutations that confer resistance to anhydrotetracycline (Atr) and resistance to heated chlortetracycline (Ctr) were isolated and characterized. All of these Atr mutations are located in the Tn10 tet region; the majority (18 of 20) have no effect on tetR repressor function. Atr mutations can increase, reduce, or eliminate the phenotypic expression of plasmid tetracycline resistance (Tcr). IS insertions that result in an Atr Tcs phenotype are clustered in a 150-base-pair promoter-proximal region of the tetA resistance gene. Some Atr mutations reduce expression of the tetA gene by altering either the tetR repressor or the tetA promoter. In addition, it appears that E. coli cannot tolerate constitutive expression of the wild-type tetA gene from a multicopy plasmid containing a tetR deletion. These observations support the proposal that high level expression of the 36-kilodalton tetA gene product inhibits the growth of E. coli. We speculate that this inhibition is related to the interaction of the tetA gene product with the cytoplasmic membrane.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6307969&dopt=Abstract antibiotics, tetracycline




Mol Microbiol. 1994 Jan;11(2):403-15.
The Clostridium perfringens Tet P determinant comprises two overlapping genes: tetA(P), which mediates active tetracycline efflux, and tetB(P), which is related to the ribosomal protection family of tetracycline-resistance determinants.

Sloan J, McMurry LM, Lyras D, Levy SB, Rood JI.

Department of Microbiology, Monash University, Clayton, Australia.

The complete nucleotide sequence and mechanism of action of the tetracycline-resistance determinant, Tet P, from Clostridium perfringens has been determined. Analysis of the 4.4 kb of sequence data revealed the presence of two open reading frames, designated as tetA(P) and tetB(P). The tetA(P) gene appears to encode a 420 amino acid protein (molecular weight 46,079) with twelve transmembrane domains. This gene was shown to be responsible for the active efflux of tetracycline from resistant cells. Although there was some amino acid sequence similarity between the putative TetA(P) protein and other tetracycline efflux proteins, analysis suggested that TetA(P) represented a different type of efflux protein. The tetB(P) gene would encode a putative 652 amino acid protein (molecular weight 72,639) with significant sequence similarity to Tet(M)-like cytoplasmic proteins that specify a ribosomal-protection tetracycline-resistance mechanism. In both C. perfringens and Escherichia coli, tetB(P) encoded low-level resistance to tetracycline and minocycline whereas tetA(P) only conferred tetracycline resistance. The tetA(P) and tetB(P) genes appeared to be linked in an operon, which represented a novel genetic arrangement for tetracycline-resistance determinants. It is proposed that tetB(P) evolved from the conjugative transfer into C. perfringens of a tet(M)-like gene from another bacterium.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8170402&dopt=Abstract antibiotics, tetracycline




J Clin Pathol. 1976 Dec;29(12):1097-100.
Sensitivity of Brucella spp to tetracycline and its analogues.

Farrell ID, Hinchliffe PM, Robertson L.

The sensitivity to eight tetracyclines of 100 strains of brucellae, comprising strains of Brucella abortus, Br. melitensis, and Br. suis, was determined. Demethylchlortetracycline was the most effecitve against all the groups of brucellae, whereas oxytetracycline and chlortetracycline were the least effective. The mean MIC value for demethylchlortetracycline, doxycycline, lymecycline, and tetracycline was less than or equal to 1 mug/ml. Strains of Br. abortus biotype 2 and Br. suis were the most sensitive strains examined.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=827554&dopt=Abstract antibiotics, tetracycline




Oral Microbiol Immunol. 1996 Aug;11(4):282-8.
Detection and prevalence of the tetracycline resistance determinant Tet Q in the microbiota associated with adult periodontitis.

Lacroix JM, Walker CB.

Periodontal Disease Research Center, College of Dentistry, University of Florida, Gainesville, USA.

Subgingival plaque samples were collected from 68 patients with a history of moderate to severe adult periodontitis and enumerated on Trypticase-soy blood agar plates, with and without tetracycline at 4 micrograms/ml. Each different colony morphotype was enumerated, and a representative colony was subcultured for identification and examined for the tetracycline resistance gene tet(Q) by polymerase chain reaction (PCR) amplification and DNA hybridization, using a fragment of tetA(Q)2 from Bacteroides fragilis 1126. PCR primers (5'-GGCTTCTACGACATCTATTA-3' and 5'-CATCAACATTTATCTCTCTG-3') were chosen to amplify a 755 bp region of tet(Q). The subgingival plaque samples were also tested by PCR. Approximately 12% of the total cultivable flora was resistant to tetracycline, and the percentage of the tetracycline-resistant cultivable flora with the tet(Q) gene varied greatly from one patient to another with a range from 0.0 to 67%. Half of the 68 subgingival plaque samples were positive or weakly positive for tet(Q) by PCR. Approximately 15% of the 210 isolates subcultured with resistance to tetracycline, (> or = 4 micrograms/ml) contained tet(Q), and 60% contained tet(M). All of the tet(Q)-resistant isolates were gram-negative anaerobic bacilli and included all of the Prevotella and Bacteroides isolates.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9002882&dopt=Abstract antibiotics, tetracycline




Geburtshilfe Frauenheilkd. 1977 Sep;37(9):788-92.
[The limits of tetracycline treatment in infections of the vagina (author's transl)]

[Article in German]

Bauernfeind A, Burrows J, Petermuller C.

The minimal inhibition concentration of Tetracycline was tested in 177 strains of gram positive and gram negative species of bacteria from the vagina which were found to be resistant to Tetracycline in the Agardiffusion Test. 170 of the 177 strains (96%) were inhibited with a Tetracycline concentration of 512 microgram/ml. Six Klebsiella-enterobacter strains and one proteus morgaini strain needed a minimal inhibition concentration of 1024 microgram/ml. For a successful local treatment of vaginitis by Tetracycline against species highly resistant to Tetracycline local Tetracycline levels of 1000 microgram/ml or better have to be obtained. Concomitant preventive treatment of fungi for instance, with amphotericin containing drugs such as mysteclin is indicated.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=914023&dopt=Abstract antibiotics, tetracycline




FEBS Lett. 1997 Dec 15;419(2-3):211-4.
Roles of acidic residues in the hydrophilic loop regions of metal-tetracycline/H+ antiporter Tet(K) of Staphylococcus aureus.

Fujihira E, Kimura T, Yamaguchi A.

Department of Cell Membrane Biology, Institute of Scientific and Industrial Research, Osaka University, Japan.

Three transmembrane glutamic acid residues play essential roles in the metal-tetracycline/H+ antiporter Tet(K) of Staphylococcus aureus [Fujihira et al., FEBS Lett. 391 (1996) 243-246]. In the putative hydrophilic loop region of the Tet(K) and Tet(L) proteins, six acidic residues are conserved. Asp74, Asp200, Asp318 and Glu381 are located on the putative cytoplasmic side, and Asp39 and Glu345 on the putative periplasmic side. These residues were replaced by a neutral amino acid residue or a charge-conserved one. In contrast to the transmembrane glutamic acid residues, the replacement of the two glutamic acid residues (Glu345 and Glu381) did not affect the tetracycline resistance level. Out of the other four aspartic acid residues, the only essential residue is Asp318, any replacement of which resulted in complete loss of the tetracycline resistance and transport activity. Asp318 is located in cytoplasmic loop 10-11 in the putative 14-transmembrane-segment topology of Tet(K). In the case of the tetracycline exporters of Gram-negative bacteria, the only essential acidic residue in the cytoplasmic loop region is located in loop 2-3 [Yamaguchi et al., Biochemistry 31 (1992) 8344-8348]. It may be a general role for tetracycline efflux proteins that three transmembrane and one cytoplasmic acidic residues are mandatory for the tetracycline transport function.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9428636&dopt=Abstract antibiotics, tetracycline




Acta Pol Pharm. 1997 May-Jun;54(3):247-8.
Frequency shift analysis of tetracycline.

Nabi SA, Abu-Nameh ES, Helaleh MI, Varshney RK.

Department of Chemistry, Aligarh Muslim University, India.

A spectrophotometric determination of tetracycline is described based on the wavelength shift in the absorption maxima (lambda max 360 nm) of tetracycline solutions in water caused by the hydrogen bonding between protons of tetracycline and the oxygens of DMSO. Tetracycline was determined in the range of 0.04 to 0.18 ppm. The method was also successfully applied to spiked urine samples.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9511451&dopt=Abstract antibiotics, tetracycline