| Autor: |
Huijbers MM; Laboratory of Biochemistry, Wageningen University &Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands., Martínez-Júlvez M; Department of Biochemistry and Molecular Cell Biology and Institute for Biocomputation and Physics of Complex Systems, University of Zaragoza, Pedro Cerbuna 12, 50009, Zaragoza, Spain., Westphal AH; Laboratory of Biochemistry, Wageningen University &Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands., Delgado-Arciniega E; Laboratory of Biochemistry, Wageningen University &Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands., Medina M; Department of Biochemistry and Molecular Cell Biology and Institute for Biocomputation and Physics of Complex Systems, University of Zaragoza, Pedro Cerbuna 12, 50009, Zaragoza, Spain., van Berkel WJ; Laboratory of Biochemistry, Wageningen University &Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands. |
| Abstrakt: |
Flavoenzymes are versatile biocatalysts containing either FAD or FMN as cofactor. FAD often binds to a Rossmann fold, while FMN prefers a TIM-barrel or flavodoxin-like fold. Proline dehydrogenase is denoted as an exception: it possesses a TIM barrel-like fold while binding FAD. Using a riboflavin auxotrophic Escherichia coli strain and maltose-binding protein as solubility tag, we produced the apoprotein of Thermus thermophilus ProDH (MBP-TtProDH). Remarkably, reconstitution with FAD or FMN revealed that MBP-TtProDH has no preference for either of the two prosthetic groups. Kinetic parameters of both holo forms are similar, as are the dissociation constants for FAD and FMN release. Furthermore, we show that the holo form of MBP-TtProDH, as produced in E. coli TOP10 cells, contains about three times more FMN than FAD. In line with this flavin content, the crystal structure of TtProDH variant ΔABC, which lacks helices αA, αB and αC, shows no electron density for an AMP moiety of the cofactor. To the best of our knowledge, this is the first example of a flavoenzyme that does not discriminate between FAD and FMN as cofactor. Therefore, classification of TtProDH as an FAD-binding enzyme should be reconsidered. |
