Two thymidine kinases and one multisubstrate deoxyribonucleoside kinase salvage DNA precursors in Arabidopsis thaliana.
Deoxyribonucleotides are the building blocks of DNA and can be synthesized via de novo and salvage pathways. Deoxyribonucleoside kinases (EC 2.7.1.145) salvage deoxyribonucleosides by transfer of a phosphate group to the 5' of a deoxyribonucleoside. This salvage pathway is well characterized in mammals, but in contrast, little is known about how plants salvage deoxyribonucleosides. We show that during salvage, deoxyribonucleosides can be phosphorylated by extracts of Arabidopsis thaliana into corresponding monophosphate compounds with an unexpected preference for purines over pyrimidines. Deoxyribonucleoside kinase activities were present in all tissues during all growth stages. In the A. thaliana genome, we identified two types of genes that could encode enzymes which are involved in the salvage of deoxyribonucleosides. Thymidine kinase activity was encoded by two thymidine kinase 1 (EC 2.7.1.21)-like genes (AtTK1a and AtTK1b). Deoxyadenosine, deoxyguanosine and deoxycytidine kinase activities were encoded by a single AtdNK gene. T-DNA insertion lines of AtTK1a and AtTK1b mutant genes had normal growth, although AtTK1a AtTK1b double mutants died at an early stage, which indicates that AtTK1a and AtTK1b catalyze redundant reactions. The results obtained in the present study suggest a crucial role for the salvage of thymidine during early plant development.
Department of Cell and Organism Biology, Lund University, Lund, Sweden. clausenar@niehs.nih.gov
Anders R
AR
Clausen
Lenart
L
Girandon
Ashfaq
A
Ali
Wolfgang
W
Knecht
Elzbieta
E
Rozpedowska
Michael P B
MP
Sandrini
Erik
E
Andreasson
Birgitte
B
Munch-Petersen
Jure
J
Piškur
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D055162:Biocatalysis; D002478:Cells, Cultured; D004269:DNA, Bacterial / Q000235:genetics; D003839:Deoxyadenosines / Q000378:metabolism; D003841:Deoxycytidine / Q000378:metabolism; D003849:Deoxyguanosine / Q000378:metabolism; D003853:Deoxyribonucleosides / Q000378:metabolism*; D007527:Isoenzymes / Q000145:classification / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D016254:Mutagenesis, Insertional; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013936:Thymidine / Q000378:metabolism; D013937:Thymidine Kinase / Q000145:classification / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D003839:Deoxyadenosines; D003853:Deoxyribonucleosides; D007527:Isoenzymes; C036483:T-DNA; D003841:Deoxycytidine; D017853:Phosphotransferases (Alcohol Group Acceptor); C020018:deoxyribonucleoside kinases; C577239:At1g72040 protein, Arabidopsis; D013937:Thymidine Kinase; D003849:Deoxyguanosine; D013936:Thymidine