A Novel Fatty Acid-Binding Protein-Like Carotenoid-Binding Protein from the Gonad of the New Zealand Sea Urchin Evechinus chloroticus

Abstract

A previously uncharacterized protein with a carotenoid-binding function has been isolated and characterized from the gonad of the New Zealand sea urchin Evechinus chloroticus. The main carotenoid bound to the protein was determined by reversed phase-high performance liquid chromatography to be 9′-cis-echinenone and hence this 15 kDa protein has been called an echinenone-binding protein (EBP). Purification of the EBP in quantity from the natural source proved to be challenging. However, analysis of EBP by mass spectrometry combined with information from the Strongylocentrotus purpuratus genome sequence and the recently published E. chloroticus transcriptome database, enabled recombinant expression of wild type EBP and also of a cysteine61 to serine mutant that had improved solubility characteristics. Circular dichroism data and ab initio structure prediction suggests that the EBP adopts a 10-stranded β-barrel fold consistent with that of fatty acid-binding proteins. Therefore, EBP may represent the first report of a fatty acid-binding protein in complex with a carotenoid.

Microalgal protein AstaP is a potent carotenoid solubilizer and delivery module with a broad carotenoid binding repertoire

“…While their carotenoid-binding functions have been well-documented, structural-functional studies were limited by the necessity to isolate protein-carotenoid complexes from natural sources. Among such examples are the Carotenoid-binding protein from silkworm [35], the Echinenone-binding protein from sea urchin [36], Pectenovarin from scallop ovary [37], and AXT-binding protein Ovorubin from apple snail [38,39]. Recently, Kawasaki and co-workers have discovered a novel water-soluble AXT-binding protein, which they called AstaP, by isolating it from unicellular eukaryotic algae [40].…”

Carotenoid composition of a New Zealand (Evechinus chloroticus) and an Australian (Heliocidaris erythrogramma) sea urchin in relation to gonad colour

“…Procedures were conducted as far as possible under dim red light to minimize carotenoid oxidation (Liaaen‐Jensen, ). The carotenoids were extracted from gonad tissue as reported previously (Garama et al., ; Pilbrow, Sabherwal, Garama & Carne, ) using a method adapted from Symonds et al. ().…”

“…Procedures were conducted as far as possible under dim red light to minimize carotenoid oxidation (Liaaen-Jensen, 1965). The carotenoids were extracted from gonad tissue as reported previously Pilbrow, Sabherwal, Garama & Carne, 2014) using a method adapted from Symonds et al (2007). Lyophilized gonad tissue, 0.3 g dry weight (d/w), was blended with 5 ml of acetone using a Polytron â aggregate dispersing homogenizer (Kinematica, Lucerne, Switzerland).…”

Carotenoids in Aquatic Ecosystems and Aquaculture: A Colorful Business with Implications for Human Health

“…Difficulties to improve gonad color partly result from the fact that carotenoid deposition is complicated by the bioconversion of dietary β,β-carotene to echinenone (Tsushima, 2007). A protein with a carotenoidbinding function, echinenone-binding protein (EBP) has been isolated and characterized from the gonad of the New Zealand sea urchin Evechinus chloroticus (Pilbrow et al, 2014). Secondary structure prediction and amino acid sequence homology analyses, led the authors to suggest that this EBP is a member of the fatty acid-binding proteins (FABPs) family which again stresses a connection between carotenoids and lipids in animal tissues.…”