Figure 2.

Structural comparison of PPN NRPS-like ATRR and fungal NRPS-like ATRR. (A) The 3D structures of MiATRR and fungal ATRR. The structure of MiATRR was predicted with RoseTTAFold online (job ID 570101), and the structure of Aspergillus nidulans ATRR (UniProt ID A0A1U8QWA2) was retrieved from AlphaFold Protein Structure Database. (B) Sequence alignment of ATRR-A from A. nidulans ATRR, MiATRR, and other PPN orthologues. The 10 “pocket” sites are indicated by red inverted triangles. (C) The 3D structural alignment of the active site pocket (10 residues) between MiATRR and A. nidulans ATRR. Green, MiATRR; pink, A. nidulans ATRR. (D) The two consecutive reducing domains of NRPS-like ATRR (R₁, R₂) reduce glycine betaine to choline via the intermediate glycine betaine aldehyde.