Institution: | 1. Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan;2. Department of Biochemistry, Faculty of Medicine, Osaka Medical and Pharmaceutical University, 2-7 Daigakumachi, Takatsuki, Osaka 569-8686, Japan;3. Graduate School of Science, Osaka Metropolitan University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan;4. Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan;5. The Japan Synchrotron Radiation Research Institute (JASRI), Sayo-gun, Hyogo 679-5198, Japan;6. Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita 565-0871, Japan;7. Integrated Frontier Research for Medical Science Division, Institute for Open and Transdisciplinary Research Initiative, Osaka University, Suita, Osaka 565-0871, Japan |
Abstract: | Fatty acid kinase is necessary for the incorporation of exogenous fatty acids into membrane phospholipids. Fatty acid kinase consists of two components: a kinase component, FakA, that phosphorylates a fatty acid bound to a fatty acid-binding component, FakB. However, the molecular details underlying the phosphotransfer reaction remain to be resolved. We determined the crystal structure of the N-terminal domain of FakA bound to ADP from Thermus thermophilus HB8. The overall structure of this domain showed that the helical barrel fold is similar to the nucleotide-binding component of dihydroxyacetone kinase. The structure of the nucleotide-binding site revealed the roles of the conserved residues in recognition of ADP and Mg2+, but the N-terminal domain of FakA lacked the ADP-capping loop found in the dihydroxyacetone kinase component. Based on the structural similarity to the two subunits of dihydroxyacetone kinase complex, we constructed a model of the complex of T. thermophilus FakB and the N-terminal domain of FakA. In this model, the invariant Arg residue of FakB occupied a position that was spatially similar to that of the catalytically important Arg residue of dihydroxyacetone kinase, which predicted a composite active site in the Fatty acid kinase complex. |