InterPro domain: IPR038672

This entry represents the CpcT/CpeT biliprotein lyase, which has been shown to covalently attach chromophores to cystiene residue(s) of phycobiliproteins [ 1 , 2 ]. These proteins contain a conserved motif PYR in the amino terminal half of the protein that may be functionally important. In the chromatically adapting cyanobacterium Fremyella diplosiphon, the proteins have been shown to be induced by green light, as part of the cpeCDESTR operon [ 3 ].

Structurally, CpcT forms a dimer and adopts a calyx-shaped beta-barrel fold. Each CpcT subunit adopts a conical, goblet-shaped beta-barrel with 10 anti-parallel beta-strands; this fold is characteristic for the FABP subfamily of the calycin superfamily.

1. Lyase activities of CpcS- and CpcT-like proteins from Nostoc PCC7120 and sequential reconstitution of binding sites of phycoerythrocyanin and phycocyanin beta-subunits. J. Biol. Chem. 282, 34093-103
2. Identification and characterization of a new class of bilin lyase: the cpcT gene encodes a bilin lyase responsible for attachment of phycocyanobilin to Cys-153 on the beta-subunit of phycocyanin in Synechococcus sp. PCC 7002. J. Biol. Chem. 281, 17768-78
3. CpeR is an activator required for expression of the phycoerythrin operon (cpeBA) in the cyanobacterium Fremyella diplosiphon and is encoded in the phycoerythrin linker-polypeptide operon (cpeCDESTR). Mol. Microbiol. 44, 1517-31