Structural characterization and antioxidant potential of phycocyanin from the cyanobacterium Geitlerinema sp. H8DM

We are reporting characterization of phycocyanin (PC), a prime light harvesting pigment, composed of nearly the same molecular weight of alpha- (17.5 kDa) and beta- (18.1 kDa) subunits in Geitlerinema sp. H8DM. Phycocyanin was purified using ammonium sulfate and anionic exchange chromatography. The fluorescence emission spectrum of PC was 637 nm when excited over 589 nm, which denoted integrity and functionality of protein structure. PC was depicted as a single subunit of ~18 kDa based on SDS-PAGE. However, similarity between both subunits was proven by two spots on gel using two dimensional gel electrophoresis. MALDI ToF/ToF showed structure similarities with alpha and beta subunits of PC. Urea induced Gibbs free energy denoted that folding and structural stability of this pigment is similar to phycocyanin of other species. Biophysical properties of peptide sequence were analyzed for several parameters and 3D model for its correlation as antioxidant. Furthermore, verification of in-silico data of PC was done by in vitro anti-oxidant assays. Hence, due to high availability, stability and antioxidant properties it can be used for auxiliary applications as colorant and therapeutic agent against oxidative stress.