PROSITE documentation PDOC00581

Riboflavin synthase alpha chain lumazine-binding repeat profile


Riboflavin synthase (RS-α) catalyzes the biosynthesis of riboflavin (vitamin B2) by dismutation of 6,7-dimethyl-8-(1'-D-ribityl)lumazine (Lum) (EC Riboflavin synthases of bacteria and fungi are structurally and evolutionary related to antenna proteins involved in bioluminescence of marine bacteria [1,2]. These proteins seem to have evolved from the duplication of a domain of about 100 residues, the lumazine-binding repeat.

The 3D structure of RS-α, which is an asymmetric homotrimer, shows that both domains form a 6-stranded antiparallel β-barrel (see <PDB:1PKV>) [3], while a C-terminal helix is involved in trimerization. The Lum-binding domain of RS-α forms two Greek-key folds with the topology BBHBBBHB, where most of the substrate binding sites are located in β-strands (B) 4 and 5 and in helix (H) 2 [3,4,5].

Some proteins known to contain a lumazine-binding repeat:

  • Riboflavin synthase α chain (EC (gene ribC in Escherichia coli, ribB in Bacillus subtilis and Photobacterium leiognathi, RIB5 in yeast). This enzyme synthesizes riboflavin from two molecules of Lum, a pteridine-derivative.
  • Photobacterium phosphoreum lumazine protein (LumP) (gene luxL). LumP is a protein that modulates the color of the bioluminescence emission of bacterial luciferase. In the presence of LumP, light emission is shifted to higher energy values (shorter wavelength). LumP binds non-covalently to 6,7-dimethyl-8-(1'-D-ribityl)lumazine.
  • Vibrio fischeri yellow fluorescent protein (YFP) (gene luxY). Like LumP, YFP modulates light emission but towards a longer wavelength. YFP binds non-covalently to FMN.

The profile we developed covers the entire lumazine-binding repeat.

Last update:

December 2005 / Pattern removed, profile added and text revised.

Technical section

PROSITE method (with tools and information) covered by this documentation:

LUMAZINE_BIND, PS51177; Riboflavin synthase alpha chain lumazine-binding repeat profile  (MATRIX)


1AuthorsO'Kane D.J., Woodward B., Lee J., Prasher D.C.
TitleBorrowed proteins in bacterial bioluminescence.
SourceProc. Natl. Acad. Sci. U.S.A. 88:1100-1104(1991).
PubMed ID1996310

2AuthorsO'Kane D.J., Prasher D.C.
TitleEvolutionary origins of bacterial bioluminescence.
SourceMol. Microbiol. 6:443-449(1992).
PubMed ID1560772

3AuthorsMeining W., Eberhardt S., Bacher A., Ladenstein R.
TitleThe structure of the N-terminal domain of riboflavin synthase in complex with riboflavin at 2.6A resolution.
SourceJ. Mol. Biol. 331:1053-1063(2003).
PubMed ID12927541

4AuthorsTruffault V., Coles M., Diercks T., Abelmann K., Eberhardt S., Luttgen H., Bacher A., Kessler H.
TitleThe solution structure of the N-terminal domain of riboflavin synthase.
SourceJ. Mol. Biol. 309:949-960(2001).
PubMed ID11399071

5AuthorsGerhardt S., Schott A.K., Kairies N., Cushman M., Illarionov B., Eisenreich W., Bacher A., Huber R., Steinbacher S., Fischer M.
TitleStudies on the reaction mechanism of riboflavin synthase: X-ray crystal structure of a complex with 6-carboxyethyl-7-oxo-8-ribityllumazine.
SourceStructure 10:1371-1381(2002).
PubMed ID12377123

PROSITE is copyright. It is produced by the SIB Swiss Institute Bioinformatics. There are no restrictions on its use by non-profit institutions as long as its content is in no way modified. Usage by and for commercial entities requires a license agreement. For information about the licensing scheme send an email to
Prosite License or see: prosite_license.html.


View entry in original PROSITE document format
View entry in raw text format (no links)