InterPro domain: IPR017825

This domain is often repeated twice within the same polypeptide, as is observed in Archaea, Thermus, Sphingobacteria [ 1 ] and Fungi. In the fungal sequences, this tandem domain pair is observed as the N-terminal half of a bifunctional protein [ 2 ], where it has been characterised as a lycopene beta-cyclase and the C-terminal half is a phytoene synthetase. In Myxococcus and Actinobacterial genomes this domain appears as a single polypeptide, tandemly repeated and usually in a genomic context consistent with a role in carotenoid biosynthesis. One member of this family has been annotated as a lycopene beta-cyclase [ 3 ]. The domain is generally hydrophobic with a number of predicted membrane spanning segments and contains a distinctive motif (hPhEEhhhhhh). In certain sequences one of either the proline or glutamates may vary, but always one of the tandem pair appear to match this canonical sequence exactly.

1. A carotenoid synthesis gene cluster from Algoriphagus sp. KK10202C with a novel fusion-type lycopene beta-cyclase gene. Mol. Genet. Genomics 276, 79-86
2. A bifunctional enzyme with lycopene cyclase and phytoene synthase activities is encoded by the carRP gene of Mucor circinelloides. Eur. J. Biochem. 267, 5509-19
3. Fusion-type lycopene beta-cyclase from a thermoacidophilic archaeon Sulfolobus solfataricus. Biochem. Biophys. Res. Commun. 305, 586-91