Phylogenetic and crystallographic analysis of Nostoc phycocyanin having blue-shifted spectral properties

Assembly of allophycocyanin from individual subunits: involvement of apo-form in the formation of trimers

In cyanobacteria and red algae, allophycocyanin (APC), as well as other phycobiliproteins, is involved in the energy transfer of photosystems. Since APC is a potent fluorescent protein for imaging and biomedical applications, it is necessary to obtain purified protein in large quantities, which is currently possible by biosynthesis in bacterial systems. Here we emphasize the challenges of obtaining the trimeric form of the protein from α-APC and β-APC subunits of allophycocyanin in vitro. This approach allowed us to study the individual subunits and to perform assembly of allophycocyanin trimers in vitro. Using different spectroscopic techniques, we detected the heterogeneity of the synthesized β-APC and showed the possibility that not only holo-forms may be involved in trimer formation. Data allowed us to provide additional arguments in favor of excitonic coupling of chromophores in APC trimers.

Microalgae: A Promising Source of Bioactive Phycobiliproteins

Phycobiliproteins are photosynthetic light-harvesting pigments isolated from microalgae with fluorescent, colorimetric and biological properties, making them a potential commodity in the pharmaceutical, cosmetic and food industries. Hence, improving their metabolic yield is of great interest. In this regard, the present review aimed, first, to provide a detailed and thorough overview of the optimization of culture media elements, as well as various physical parameters, to improve the large-scale manufacturing of such bioactive molecules. The second section of the review offers systematic, deep and detailed data about the current main features of phycobiliproteins. In the ultimate section, the health and nutritional claims related to these bioactive pigments, explaining their noticeable potential for biotechnological uses in various fields, are examined.

Crystal structure of Synechococcus phycocyanin: implications of light-harvesting and antioxidant properties

Phycobiliproteins is a family of chromophore-containing proteins having light-harvesting and antioxidant capacity. The phycocyanin (PC) is a brilliant blue coloured phycobiliprotein, found in rod structure of phycobilisome and has been widely studied for their therapeutic and fluorescent properties. In the present study, the hexameric assembly structure of phycocyanin (Syn-PC) from Synechococcus Sp. R42DM is characterized by X-ray crystallography to understand its light-harvesting and antioxidant properties. The crystal structure of Syn-PC is solved with 2.15 Å resolution and crystallographic R-factors, Rwork/Rfree, 0.16/0.21. The hexamer of Syn-PC is formed by heterodimer of two polypeptide chains, namely, α- and β-subunits. The structure is analysed at atomic level to reveal the chromophore microenvironment and possible light energy transfer mechanism in Syn-PC. The chromophore arrangement in hexamer, deviation angle and distance between the chromophore contribute to the energy transfer efficiency of protein. The structural attributes responsible for the antioxidant potential of Syn-PC are recognized and annotated on its 3-dimensional structure.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03665-1.

Exploring the structural aspects and therapeutic perspectives of cyanobacterial phycobiliproteins

Phycobiliproteins (PBPs) of cyanobacteria and algae possess unique light harvesting capacity which expand the photosynthetically active region (PAR) and allow them to thrive in extreme niches where higher plants cannot. PBPs of cyanobacteria/algae vary in abundance, types, amino acid composition and in structure as a function of species and the habitat that they grow in. In the present review, the key aspects of structure, stability, and spectral properties of PBPs, and their correlation with ecological niche of cyanobacteria are discussed. Besides their role in light-harvesting, PBPs possess antioxidant, anti-aging, neuroprotective, hepatoprotective and anti-inflammatory properties, which can be used in therapeutics. Recent developments in therapeutic applications of PBPs are reviewed with special focus on 'route of PBPs administration' and 'therapeutic potential of PBP-derived peptide and chromophores'.

Phycobiliproteins from Anabaena variabilis CCC421 and its production enhancement strategies using combinatory evolutionary algorithm approach

The production of phycobiliproteins (PBPs) from cyanobacteria represents both the industrial application and their commercial value. In this study, the capability of Anabaena variabilis CCC421 for the production of PBPs was evaluated which was further improved by optimization of selected BG-11 medium components viz. FAC, K₂HPO₄ and trace metals. A design matrix approach using evolutionary algorithm comprised of genetic-algorithm (GA) and fuzzy-logic-methodology (FLM), i.e., GA-Fuzzy, was used for the optimization. The maximum production of PBPs obtained with combinatory approach of GA-Fuzzy was 408.5 mg/L at an optimum combination of factors (FAC 0.153 g/L, K₂HPO₄ 0.2 g/L and Trace metals 0.5 ml/L) which was a 2.13 fold more than the control medium. This novel approach is very useful for modulating biological processes since various nutrients and metabolites have greater influence on these processes.

Revisiting high-resolution crystal structure of Phormidium rubidum phycocyanin

The crystal structure of phycocyanin (pr-PC) isolated from Phormidium rubidum A09DM (P. rubidum) is described at a resolution of 1.17 Å. Electron density maps derived from crystallographic data showed many clear differences in amino acid sequences when compared with the previously obtained gene-derived sequences. The differences were found in 57 positions (30 in α-subunit and 27 in β-subunit of pr-PC), in which all residues except one (β145Arg) are not interacting with the three phycocyanobilin chromophores. Highly purified pr-PC was then sequenced by mass spectrometry (MS) using LC-MS/MS. The MS data were analyzed using two independent proteomic search engines. As a result of this analysis, complete agreement between the polypeptide sequences and the electron density maps was obtained. We attribute the difference to multiple genes in the bacterium encoding the phycocyanin apoproteins and that the gene sequencing sequenced the wrong ones. We are not implying that protein sequencing by mass spectrometry is more accurate than that of gene sequencing. The final 1.17 Å structure of pr-PC allows the chromophore interactions with the protein to be described with high accuracy.