Characterization of porphobilinogen deaminase mutants reveals that arginine-173 is crucial for polypyrrole elongation mechanism
Bustad, Helene J.; Kallio, Juha P.; Laitaoja, Mikko; Karen Toska, Karen Toska; Kursula, Inari; Martinez, Aurora; Jänis, Janne (2021-02-06)
Helene J. Bustad, Juha P. Kallio, Mikko Laitaoja, Karen Toska, Inari Kursula, Aurora Martinez, Janne Jänis, Characterization of porphobilinogen deaminase mutants reveals that arginine-173 is crucial for polypyrrole elongation mechanism, iScience, Volume 24, Issue 3, 2021, 102152, ISSN 2589-0042, https://doi.org/10.1016/j.isci.2021.102152
© 2021 The Author(s). This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
https://creativecommons.org/licenses/by/4.0/
https://urn.fi/URN:NBN:fi-fe2021051730150
Tiivistelmä
Abstract
Porphobilinogen deaminase (PBGD), the third enzyme in the heme biosynthesis, catalyzes the sequential coupling of four porphobilinogen (PBG) molecules into a heme precursor. Mutations in PBGD are associated with acute intermittent porphyria (AIP), a rare metabolic disorder. We used Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to demonstrate that wild-type PBGD and AIP-associated mutant R167W both existed as holoenzymes (Eholo) covalently attached to the dipyrromethane cofactor, and three intermediate complexes, ES, ES₂, and ES₃, where S represents PBG. In contrast, only ES₂ was detected in AIP-associated mutant R173W, indicating that the formation of ES₃ is inhibited. The R173W crystal structure in the ES₂-state revealed major rearrangements of the loops around the active site, compared to wild-type PBGD in the Eholo-state. These results contribute to elucidating the structural pathogenesis of two common AIP-associated mutations and reveal the important structural role of Arg173 in the polypyrrole elongation mechanism.
Kokoelmat
- Avoin saatavuus [31995]