Microalgal protein AstaP is a potent carotenoid solubilizer and delivery module with a broad carotenoid binding repertoire. (10th October 2021)

• Record Type: Journal Article
• Authors: Slonimskiy, Yury B.; Egorkin, Nikita A.; Friedrich, Thomas; Maksimov, Eugene G.; Sluchanko, Nikolai N.
• Is Part Of: FEBS journal. Volume 289:Number 4(2022)
• Page Start: 999
• Page End: 1022
• Publication Date: 2021-10-10
• Subjects: AlphaFold -- antioxidant -- carotenoprotein -- liposome -- SEC‐MALS; Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pathology, Molecular -- Periodicals; 572
• DOI: 10.1111/febs.16215
• Languages: English
• ISSNs: 1742-464X

Abstract

Abstract : Carotenoids are lipophilic substances with many biological functions, from coloration to photoprotection. Being potent antioxidants, carotenoids have multiple biomedical applications, including the treatment of neurodegenerative disorders and retina degeneration. Nevertheless, the delivery of carotenoids is substantially limited by their poor solubility in the aqueous phase. Natural water‐soluble carotenoproteins can facilitate this task, necessitating studies on their ability to uptake and deliver carotenoids. One such promising carotenoprotein, AstaP (astaxanthin‐binding protein), was recently identified in eukaryotic microalgae, but its structure and functional properties remained largely uncharacterized. By using a correctly folded recombinant protein, here we show that AstaP is an efficient carotenoid solubilizer that can stably bind not only astaxanthin but also zeaxanthin, canthaxanthin, and, to a lesser extent, β‐carotene, that is, carotenoids especially valuable to human health. AstaP accepts carotenoids provided as acetone solutions or embedded in membranes, forming carotenoid–protein complexes with an apparent stoichiometry of 1:1. We successfully produced AstaP holoproteins in specific carotenoid‐producing strains of Escherichia coli, proving it is amenable to cost‐efficient biotechnology processes. Regardless of the carotenoid type, AstaP remains monomeric in both apo‐ and holoform, while its rather minimalistic mass (~ 20 kDa) makes it an especially attractive antioxidant delivery module. In vitro, AstaP transfers different carotenoids to liposomes and to unrelated proteins from cyanobacteria, which can modulate their photoactivity and/or oligomerization. These findings expand the toolkit of the characterized carotenoid binding proteins and outline the perspective of the use of AstaP as a unique monomeric antioxidant nanocarrier with an extensive carotenoid binding repertoire. Abstract : Carotenoids are potent antioxidants with various applications, whose solubility and targeted delivery are facilitated by natural water‐soluble carotenoproteins. Focusing on the recombinant astaxanthin‐binding protein (AstaP) from microalgae, we show that it forms monomers efficiently solubilizing different carotenoids valuable to human health. AstaP participates in carotenoid transfer to the liposomes and unrelated proteins, modulating their photoactivity and/or oligomerization, and is therefore an attractive antioxidant delivery module with an extensive carotenoid binding repertoire.