Mutations within the putative active site of heterodimeric deoxyguanosine kinase block the allosteric activation of the deoxyadenosine kinase subunit.
Replacement of the Asp-84 residue of the deoxyguanosine kinase subunit of the tandem deoxyadenosine kinase/ deoxyguanosine kinase (dAK/dGK) from Lactobacillus acidophilus R-26 by Ala, Asn, or Glu produced increased Km values for deoxyguanosine on dGK. However, it did not seem to affect the binding of Mg-ATP. The Asp-84 dGK replacements had no apparent effect on the binding of deoxyadenosine by dAK. However, the mutant dGKs were no longer inhibited by dGTP, normally a potent distal endproduct inhibitor of dGK. Moreover, the allosteric activation of dAK activity by dGTP or dGuo was lost in the modified heterodimeric dAK/dGK enzyme. Therefore, it seems very likely that Asp-84 participates in dGuo binding at the active site of the dGK subunit of dAK/dGK from Lactobacillus acidophilus R-26.
Park
Inshik
I
Faculty of Food Science, Dong-A University, Pusan 604-714, Korea. ispark@mail.donga.ac.kr
Ives
David H
DH
D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D001483:Base Sequence; D020134:Catalytic Domain / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D019281:Dimerization; D007779:Lactobacillus acidophilus / Q000201:enzymology* / Q000235:genetics*; D016297:Mutagenesis, Site-Directed; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D021122:Protein Subunits; D017386:Sequence Homology, Amino Acid
D004269:DNA, Bacterial; D021122:Protein Subunits; D017853:Phosphotransferases (Alcohol Group Acceptor); C019165:deoxyguanosine kinase