Structural basis for feedback inhibition of the deoxyribonucleoside salvage pathway: studies of the Drosophila deoxyribonucleoside kinase.
Deoxyribonucleoside kinases are feedback inhibited by the final products of the salvage pathway, the deoxyribonucleoside triphosphates. In the present study, the mechanism of feedback inhibition is presented based on the crystal structure of a complex between the fruit fly deoxyribonucleoside kinase and its feedback inhibitor deoxythymidine triphosphate. The inhibitor was found to be bound as a bisubstrate inhibitor with its nucleoside part in the nucleoside binding site and with its phosphate groups partially occupying the phosphate donor site. The overall structure of the enzyme--inhibitor complex is very similar to the enzyme--substrate complexes with deoxythymidine and deoxycytidine, except for a conformational change within a region otherwise directly involved in catalysis. This conformational change involves a magnesium ion, which is coordinated in the inhibitor complex to the phosphates and to the primary base, Glu52, that normally is positioned close to the 5'-OH of the substrate deoxyribose.
Department of Molecular Biology, Swedish University of Agricultural Sciences, Box 590, Biomedical Center, S-751 24 Uppsala, Sweden.
Nils Egil
NE
Mikkelsen
Kenth
K
Johansson
Andreas
A
Karlsson
Wolfgang
W
Knecht
Gorm
G
Andersen
Jure
J
Piskur
Birgitte
B
Munch-Petersen
Hans
H
Eklund
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D003853:Deoxyribonucleosides / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000201:enzymology* / Q000235:genetics; D005246:Feedback; D007700:Kinetics; D008958:Models, Molecular; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055672:Static Electricity; D013942:Thymine Nucleotides / Q000378:metabolism
D003853:Deoxyribonucleosides; D011994:Recombinant Proteins; D013942:Thymine Nucleotides; D000255:Adenosine Triphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C020018:deoxyribonucleoside kinases; C019165:deoxyguanosine kinase; C024157:thymidine 5'-triphosphate