Homologous Superfamily

Orange carotenoid-binding protein, N-terminal domain superfamily (IPR036917)

Short name: Orange_carotenoid-bd_N_sf

Overlapping entries


Carotenoids such as beta-carotene, lycopene, lutein and beta-cryptoxanthine are produced in plants and certain bacteria, algae and fungi, where they function as accessory photosynthetic pigments and as scavengers of oxygen radicals for photoprotection. They are also essential dietary nutrients in animals. Orange carotenoid-binding proteins (OCP) were first identified in cyanobacterial species, where they occur associated with phycobilisome in the cellular thylakoid membrane. These proteins function in photoprotection, and are essential for inhibiting white and blue-green light non-photochemical quenching (NPQ) [PMID: 17307930, PMID: 16531492]. Carotenoids improve the photoprotectant activity by broadening OCP's absorption spectrum and facilitating the dissipation of absorbed energy. OCP acts as a homodimer, and binds one molecule of carotenoid (3'-hydroxyechinenone) and one chloride ion per subunit, where the carotenoid binding site is lined with a striking number of methionine residues. The carotenoid 3'-hydroxyechinenone is not found in higher plants. OCP has two domains: an N-terminal helical domain and a C-terminal domain that resembles a NTF2 (nuclear transport factor 2) domain. OCP can be proteolytically cleaved into a red form (RCP), which lacks 15 residues from the N terminus and approximately 150 residues from the C terminus [PMID: 16034528].

This entry represents the N-terminal domain superfamily found predominantly in prokaryotic orange carotenoid proteins and related carotenoid-binding proteins. It adopts an alpha-helical structure consisting of two four-helix bundles [PMID: 12517340].

GO terms

Biological Process

GO:0016037 light absorption

Molecular Function

GO:0031404 chloride ion binding

Cellular Component

GO:0030089 phycobilisome

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.