Abstract
Peridinin-Chlorophyll a-Proteins (PCP) are the major light harvesting proteins in photosynthetic dinoflagellates. PCP shows great variation in protein length, pigment ratio, sequence, and spectroscopic properties. PCP conjugates (PerCP) are widely used as fluorescent probes for cellular and tissue analysis in the biomedical field. PCP consists of a peridinin carotenoid; thereby, it can potentially be used as a bioactive compound in pharmaceutical applications. However, the biological activities of PCP are yet to be explored. In this study, we extracted, purified, and partially characterised the PCP from Symbiodinium tridacnidorum (CS-73) and explored its antioxidant, anti-cancer and anti-inflammation bioactivities. The PCP was purified using an ÄKTA™ PURE system and predicted to be of 17.3 kDa molecular weight (confirmed as a single band on SDS-PAGE) with an isoelectric point (pI) 5.6. LC-MS/MS and bioinformatic analysis of purified PCP digested with trypsin indicated it was 164 amino acids long with >90% sequence similarity to PCP of SymA3.s6014_g3 (belonging to clade A of Symbiodinium sp.) confirmed with 59 peptide combinations matched across its protein sequence. The spectroscopic properties of purified PCP showed a slight shift in absorption and emission spectra to previously documented analysis in Symbiodinium species possibly due to variation in amino acid sequences that interact with chl a and peridinin. Purified PCP consisted of a 19-amino-acid-long signal peptide at its N terminal and nine helixes in its secondary structure, with several protein binding sites and no DNA/RNA binding site. Furthermore, purified PCP exhibited antioxidant and in vitro anti-inflammation bioactivities, and anti-cancer activities against human metastatic breast adenocarcinoma (MDA-MB-231) and human colorectal (HTC-15) cancer cell lines. Together, all these findings present PCP as a promising candidate for continued investigations for pharmaceutical applications to cure chronic diseases, apart from its existing application as a fluorescent-probe.
Highlights
Licensee MDPI, Basel, Switzerland.Peridinin-Chlorophyll a-Protein (PCP) is a water-soluble light harvesting complex (LHC) protein in photosynthetic dinoflagellates [1]
Conclusions evaluation of Peridinin-Chlorophyll a-Proteins (PCP) against cancerous cells in terms of antioxidant, antitumor, and antiThis is the first report of the extraction, purification, inflammatory activities
Of molecular weight kDa, and amino acids that exhibited several proevaluation of PCP against cancerous cells in terms of antioxidant, antitumor, an tein binding regions, but no DNA/RNA binding site supports its suitability in designing inflammatory activities
Summary
Peridinin-Chlorophyll a-Protein (PCP) is a water-soluble light harvesting complex (LHC) protein in photosynthetic dinoflagellates [1]. Dinoflagellates represent a potential source of peridinin carotenoids in the form of PCP, which has a structure similar to that of fucoxanthin; its biological activities have not been explored sufficiently. The dinoflagellate Amphidinium carterae possesses a trimeric PCP complex, which is formed by three copies of the monomeric PCP [16]. PCP characterisation in dinoflagellates has largely focused on determining spectroscopic properties and photosynthetic energy transfer analysis. It is imperative to purify and characterise PCP from Symbiodinium sp., which exhibits multiple forms of PCP, exploring its biological activities to enhance its pharmaceutical applications as marine bio-products. The bioactivities of the purified PCP including antioxidant, cytotoxicity, and anti-inflammation were examined to explore its potential use in pharmaceutical applications
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