The structural principles underlying molybdenum insertase complex assembly

Protein Sci. 2023 Sep;32(9):e4753. doi: 10.1002/pro.4753.


Within the cell, the trace element molybdenum (Mo) is only biologically active when complexed either within the nitrogenase-specific FeMo cofactor or within the molybdenum cofactor (Moco). Moco consists of an organic part, called molybdopterin (MPT) and an inorganic part, that is, the Mo-center. The enzyme which catalyzes the Mo-center formation is the molybdenum insertase (Mo-insertase). Mo-insertases consist of two functional domains called G- and E-domain. The G-domain catalyzes the formation of adenylated MPT (MPT-AMP), which is the substrate for the E-domain, that catalyzes the actual molybdate insertion reaction. Though the functions of E- and G-domain have been elucidated to great structural and mechanistic detail, their combined function is poorly characterized. In this work, we describe a structural model of the eukaryotic Mo-insertase Cnx1 complex that was generated based on cross-linking mass spectrometry combined with computational modeling. We revealed Cnx1 to form an asymmetric hexameric complex which allows the E- and G-domain active sites to align in a catalytic productive orientation toward each other.

Keywords: biosynthesis complex; molybdenum cofactor; molybdenum insertase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis Proteins* / chemistry
  • Arabidopsis* / chemistry
  • Calnexin / chemistry
  • Calnexin / metabolism
  • Coenzymes / chemistry
  • Metalloproteins* / chemistry
  • Molybdenum / metabolism
  • Pteridines / chemistry


  • Arabidopsis Proteins
  • Calnexin
  • Molybdenum
  • Coenzymes
  • Metalloproteins
  • Pteridines