Crystal structures of Aspergillus oryzae Rib2 deaminase: the functional mechanism involved in riboflavin biosynthesis
Journal
IUCrJ
Journal Volume
8
Journal Volume
8
Journal Issue
4
Journal Issue
4
Pages
549
Start Page
549
End Page
558
ISSN
20522525
Date Issued
2021-07
Author(s)
Abstract
Riboflavin serves as the direct precursor of the FAD/FMN coenzymes and is biosynthesized in most prokaryotes, fungi and plants. Fungal Rib2 possesses a deaminase domain for deamination of pyrimidine in the third step of riboflavin biosynthesis. Here, four high-resolution crystal structures of a Rib2 deaminase from Aspergillus oryzae (AoRib2) are reported which display three distinct occluded, open and complex forms that are involved in substrate binding and catalysis. In addition to the deaminase domain, AoRib2 contains a unique C-terminal segment which is rich in charged residues. Deletion of this unique segment has no effect on either enzyme activity or protein stability. Nevertheless, the C-terminal αF helix preceding the segment plays a role in maintaining protein stability and activity. Unexpectedly, AoRib2 is the first mononucleotide deaminase found to exist as a monomer, perhaps due to the assistance of its unique longer loops (Lβ1-β2, LαB-β3 and LαC-β4). These results form the basis for a molecular understanding of riboflavin biosynthesis in fungi and might assist in the development of antibiotics.
Subjects
riboflavin biosynthesis
Rib2
deaminases
substrate binding
crystal structure
SDGs
Publisher
International Union of Crystallography ({IUCr})
Type
journal article