Deletion and Site-directed Mutagenesis of the ATP-binding Motif (P-loop) in the Bifunctional Murine Atp-Sulfurylase/Adenosine 5′-Phosphosulfate Kinase Enzyme
| Autor: | Andrea T. Deyrup, Srinivasan Krishnan, B. N. Cockburn, Nancy B. Schwartz |
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| Rok vydání: | 1998 |
| Předmět: |
ATP-binding motif
MAP3K7 Polymerase Chain Reaction Biochemistry MAP2K7 Mice Adenosine Triphosphate Multienzyme Complexes Animals Point Mutation Cloning Molecular Kinase activity Site-directed mutagenesis Molecular Biology Sequence Deletion Alanine Binding Sites biology Kinase Cyclin-dependent kinase 2 Brain Cell Biology Molecular biology Recombinant Proteins Sulfate Adenylyltransferase Kinetics Phosphotransferases (Alcohol Group Acceptor) Mutagenesis Site-Directed biology.protein |
| Zdroj: | Journal of Biological Chemistry. 273:9450-9456 |
| ISSN: | 0021-9258 |
| Popis: | The P-loop is a common motif found in ATP- and GTP-binding proteins. The recently cloned murine ATP-sulfurylase/adenosine 5'-phosphosulfate (APS) kinase contains a P-loop (residues 59-66) in the APS kinase portion of the bifunctional protein. A series of enzymatic assays covering the multiplicity of functions of this unique protein (reverse ATP-sulfurylase, APS kinase, and an overall assay) were used to determine the effect of deleting or altering specific residues constituting this motif. In addition to the full-length cDNA construct (1MSK), two deletion mutants that progressively shortened the N terminus by 34 amino acids (2MSK) and 70 amino acids (3MSK) were designed to examine the effects of translation initiation before (2MSK) and after (3MSK) the P-loop. The 2MSK protein possessed sulfurylase and kinase activity equivalent to the full-length construct, but 3MSK exhibited no kinase activity and reduced sulfurylase activity. In light of the evident importance of this motif, a number of site-directed mutants were designed to investigate the contribution of key residues. Mutation of a highly conserved lysine in the P-loop to alanine (K65A) or arginine (K65R) or the following threonine (T66A) to alanine ablated APS kinase activity while leaving ATP-sulfurylase activity intact. Three mutations (G59A, G62A, and G64A) addressed the role of the conserved glycines as follows: G64A showed diminished APS kinase activity only, whereas G62A had no effect on either activity. G59A caused a significant decrease in ATP-sulfurylase activity without effect on APS kinase activity. A series of highly conserved flanking cysteines (Cys-53, Cys-77, and Cys-83) were mutated to alanine, but none of these mutations showed any effect on either enzyme activity. |
| Databáze: | OpenAIRE |
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