Orange carotenoid protein

Despite their absence in phycobilisomes, carotenoids, especially the so-called secondary carotenoids such as echinenone, were presumed to play a role in cyanobacterial photoprotection. Indeed, classic biochemical approaches have led to several reports of cyanobacterial carotenoid-proteins and evidence for their photoprotective function (Kerfeld et al. 2003, Kerfeld 2004b). One of these, the water soluble orange carotenoid protein (OCP), has been structurally characterized and has recently emerged as a key player in cyanobacterial photoprotection. 

Orange carotenoid protein Conserved hypothetical protein (sir 1964) ft- OCP N terminal domain OCP C-terminal domain Hypothetical protein Hypothetical protein D- Beta carotene ketolase homolog Hydrolase... 

Bailey, S., N. Mann, C. Robinson, and D. J. Scanlan (2005). The occurrence of rapidly reversible non-photochemical quenching of chlorophyll a fluorescence in cyanobacteria. FEBS Lett 579(1) 275-280. Boulay, C., L. Abasova, C. Six, I. Vass, and D. Kirilovsky (2008a). Occurrence and function of the orange carotenoid protein in photoprotective mechanisms in various cyanobacteria. Biochim Biophys Acta 1777(10) 1344-1354. 

Kirilovsky, D. (2007). Photoprotection in cyanobacteria The orange carotenoid protein (OCP)-related non-photochemical-quenching mechanism. Photosynth Res 93 7-16. 

Polfvka, T., C. A. Kerfeld, T. Pascher, and V. Sundstrom (2005). Spectroscopic properties of the carotenoid 3 -hydroxyechinenone in the orange carotenoid protein from the cyanobacterium Arthrospira maxima. Biochemistry 44(10) 3994—4003. 

Specific carotenoid-protein complexes have been reported in plants and invertebrates (cyanobacteria, crustaceans, silkworms, etc.), while data on the existence of carotenoproteins in vertebrates are more limited. As alternatives for their water solubilization, carotenoids could use small cytosolic carrier vesicles." Carotenoids can also be present in very fine physical dispersions (or crystalline aggregates) in aqueous media of oranges, tomatoes, and carrots. Thus these physicochemical characteristics of carotenoids as well as those of other pigments are important issues for the understanding of their bioavailability. 

Lobster and shrimp dine on carotenoid-containing plankton, and the compounds become concentrated in their shells. Here the carotenoids are bound up with protein molecules, and the carotenoid-protein complex has a dark green color. When the protein is heated, it is denatured. In other words, it breaks down and disassociates from the reddish pigment, astaxanthin, which then becomes visible. To a smaller extent this is also evident in cooked carrots, which become more orange than they were before. This was another experiment my daughter and I decided to try. We cooked up some fresh carrots to see if they would become more orange. They did, but the effect was not as pronounced as it was with the shrimp, because carrots have little protein. 

Crustaceans contain carotenoids bound to protein resulting in a blue or blue-gray color. When the animal is immersed in boiling water, the carotenoid-protein bond is broken and the orange-red color of the free car-... 

Carotenoids involved in photosynthesis are bound to and help stabilize chlorophyll-protein complexes, of which various types occur in the lamellar membranes of chloroplasts (Fig. 1-10). Carotenoids also are found in organelles known as chromoplasts, which are about the size of chloroplasts and are often derived from them. For instance, lycopene (red) is in tomato fruit chromoplasts, and a- and pi-carotenes (orange) occur in carrot root chromoplasts. A great diversity of carotenoids occurs in the chromoplasts of flower petals, which is important for attracting pollinators, and fruits, which aids in seed dispersal by attracting other animals. 

Fig. 4. Overall view of the RC structure. The Cj, chains of the protein are shown as grey ribbons. Refer to color plate 7 for the colors of the cofactors which are represented as blue (heme groups), red (special pair), green (accessory bacteriochlorophylls), lilac (carotenoid), yellow (bacteriopheophytins), orange (quinones) and cyan (non-heme iron). (See also Color Plate 7)...

The surface pigmentation of marine animals is largely due to different caroteno-proteins, which may be yellow, orange, red, purple, blue, or green, depending on the structure of the complexes — the kind of carotenoid, predominantly astaxanthin, cantaxanthin, and (l-carotene, as well as the properties of the proteinaceous compo-... 

---