A few amino acid substitutions can convert deoxyribonucleoside kinase specificity from pyrimidines to purines.
In mammals, the four native deoxyribonucleosides are phosphorylated to the corresponding monophosphates by four deoxyribonucleoside kinases, which have specialized substrate specificities. These four enzymes are likely to originate from a common progenitor kinase. Insects appear to have only one multisubstrate deoxyribonucleoside kinase (dNK, EC 2.7.1.145), which prefers pyrimidine nucleosides, but can also phosphorylate purine substrates. When the structures of the human deoxyguanosine kinase (dGK, EC 2.7.1.113) and the dNK from Drosophila melanogaster were compared, a limited number of amino acid residues were identified and proposed to be responsible for the substrate specificity. Three of these key residues in Drosophila dNK were then mutagenized and the mutant enzymes were characterized regarding their ability to phosphorylate native deoxyribonucleosides and nucleoside analogs. The mutations converted the dNK substrate specificity from predominantly pyrimidine specific into purine specific. A similar scenario could have been followed during the evolution of kinases. Upon gene duplication of the progenitor kinase, only a limited number of single amino acid changes has taken place in each copy and resulted in substrate-specialized enzymes.
Knecht
Wolfgang
W
Section of Molecular Microbiology, BioCentrum-DTU, Building 301, Technical University of Denmark, DK-2800 Lyngby, Denmark. wolfgang.knecht@biocentrum.dtu.dk
Sandrini
Michael P B
MP
Johansson
Kenth
K
Eklund
Hans
H
Munch-Petersen
Birgitte
B
Piskur
Jure
J
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D003853:Deoxyribonucleosides / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D011687:Purines / Q000378:metabolism*; D011743:Pyrimidines / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D003853:Deoxyribonucleosides; D011687:Purines; D011743:Pyrimidines; C022496:pyrimidine deoxyribonucleoside kinase; D017853:Phosphotransferases (Alcohol Group Acceptor); C020018:deoxyribonucleoside kinases; C019165:deoxyguanosine kinase