Molecular characterization of thymidine kinase from Ureaplasma urealyticum: nucleoside analogues as potent inhibitors of mycoplasma growth.
Ureaplasma urealyticum (U. urealyticum), belonging to the class Mollicutes, is a human pathogen colonizing the urogenital tract and causes among other things respiratory diseases in premature infants. We have studied the salvage of pyrimidine deoxynucleosides in U. urealyticum and cloned a key salvage enzyme, thymidine kinase (TK) from U. urealyticum. Recombinant Uu-TK was expressed in E. coli, purified and characterized with regards to substrate specificity and feedback inhibition. Uu-TK efficiently phosphorylated thymidine (dThd) and deoxyuridine (dUrd) as well as a number of pyrimidine nucleoside analogues. All natural ribonucleoside/deoxyribonucleoside triphosphates, except dTTP, served as phosphate donors, while dTTP was a feedback inhibitor. The level of Uu-TK activity in U. urealyticum extracts increased upon addition of dUrd to the growth medium. Fluoropyrimidine nucleosides inhibited U. urealyticum and M. pneumoniae growth and this inhibitory effect could be reversed by addition of dThd, dUrd or deoxytetrahydrouridine to the growth medium. Thus, the mechanism of inhibition was most likely the depletion of dTTP, either via a blocked thymidine kinase reaction and/or thymidylate synthesis step and these metabolic reactions should be suitable targets for antimycoplasma chemotherapy.
Carnrot
Cecilia
C
Department of Molecular Biosciences, The Swedish University of Agricultural Sciences, The Biomedical Centre, PO Box 575, SE-751 23 Uppsala, Sweden.
Wehelie
Rahma
R
Eriksson
Staffan
S
Bölske
Göran
G
Wang
Liya
L
D000595:Amino Acid Sequence; D002455:Cell Division / Q000187:drug effects; D003001:Cloning, Molecular; D003857:Deoxyuridine / Q000378:metabolism / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics; D025461:Feedback, Physiological; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009177:Mycoplasma pneumoniae / Q000187:drug effects* / Q000254:growth & development; D009705:Nucleosides / Q000378:metabolism / Q000494:pharmacology*; D010710:Phosphates / Q000378:metabolism; D011741:Pyrimidine Nucleosides / Q000378:metabolism / Q000494:pharmacology; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D018119:Stavudine / Q000378:metabolism; D013379:Substrate Specificity; D013767:Tetrahydrouridine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism*; D013942:Thymine Nucleotides / Q000378:metabolism / Q000494:pharmacology; D016990:Ureaplasma urealyticum / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D015215:Zidovudine / Q000378:metabolism
D009705:Nucleosides; D010710:Phosphates; D011741:Pyrimidine Nucleosides; D011994:Recombinant Proteins; D013942:Thymine Nucleotides; D013767:Tetrahydrouridine; C052729:2'-deoxytetrahydrouridine; D015215:Zidovudine; D018119:Stavudine; D013937:Thymidine Kinase; C024157:thymidine 5'-triphosphate; D013936:Thymidine; D003857:Deoxyuridine