The Crystal Structure of RosB: Insights into the Reaction Mechanism of the First Member of a Family of Flavodoxin-like Enzymes

Angew Chem Int Ed Engl. 2017 Jan 19;56(4):1146-1151. doi: 10.1002/anie.201610292. Epub 2016 Dec 16.


8-demethyl-8-aminoriboflavin-5'-phosphate (AFP) synthase (RosB) catalyzes the key reaction of roseoflavin biosynthesis by forming AFP from riboflavin-5'-phosphate (RP) and glutamate via the intermediates 8-demethyl-8-formylriboflavin-5'-phosphate (OHC-RP) and 8-demethyl-8-carboxylriboflavin-5'-phosphate (HO2 C-RP). To understand this reaction in which a methyl substituent of an aromatic ring is replaced by an amine we structurally characterized RosB in complex with OHC-RP (2.0 Å) and AFP (1.7 Å). RosB is composed of four flavodoxin-like subunits which have been upgraded with specific extensions and a unique C-terminal arm. It appears that RosB has evolved from an electron- or hydride-transferring flavoprotein to a sophisticated multi-step enzyme which uses RP as a substrate (and not as a cofactor). Structure-based active site analysis was complemented by mutational and isotope-based mass-spectrometric data to propose an enzymatic mechanism on an atomic basis.

Keywords: AFP synthase; RosB; Streptomyces davawensis; roseoflavin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism*
  • Biocatalysis
  • Crystallography, X-Ray
  • Mass Spectrometry
  • Models, Molecular
  • Protein Conformation
  • Riboflavin / analogs & derivatives*
  • Riboflavin / biosynthesis
  • Riboflavin / chemistry
  • Transaminases / chemistry*
  • Transaminases / metabolism*


  • Bacterial Proteins
  • 8-amino-8-demethylriboflavin
  • Transaminases
  • RosB protein, Streptomyces davawensis
  • Riboflavin