title: Stabilization of Human Serum Albumin by the Binding of Phycocyanobilin, a Bioactive Chromophore of Blue-Green Alga Spirulina: Molecular Dynamics and Experimental Study.
abstract: Phycocyanobilin (PCB) binds with high affinity (2.2 x 106 M-1 at 25°C) to human serum albumin (HSA) at sites located in IB and IIA subdomains. The aim of this study was to examine effects of PCB binding on protein conformation and stability. Using 300 ns molecular dynamics (MD) simulations, UV-VIS spectrophotometry, CD, FT-IR, spectrofluorimetry, thermal denaturation and susceptibility to trypsin digestion, we studied the effects of PCB binding on the stability and rigidity of HSA, as well as the conformational changes in PCB itself upon binding to the protein. MD simulation results demonstrated that HSA with PCB bound at any of the two sites showed greater rigidity and lower overall and individual domain flexibility compared to free HSA. Experimental data demonstrated an increase in the α-helical content of the protein and thermal and proteolytic stability upon ligand binding. PCB bound to HSA undergoes a conformational change to a more elongated conformation in the binding pockets of HSA. PCB binding to HSA stabilizes the structure of this flexible transport protein, making it more thermostable and resistant to proteolysis. The results from this work explain at molecular level, conformational changes and stabilization of HSA structure upon ligand binding. The resultant increased thermal and proteolytic stability of HSA may provide greater longevity to HSA in plasma.
authors.affiliation: Institute of Chemistry, Technology and Metallurgy - Center for Chemistry, University of Belgrade, Belgrade, Serbia.
authors.forename: Milica
authors.initials: M
authors.lastname: Radibratovic
authors.affiliation: Center of Excellence for Molecular Food Sciences, University of Belgrade - Faculty of Chemistry, Belgrade, Serbia.
authors.forename: Simeon
authors.initials: S
authors.lastname: Minic
authors.affiliation: Center of Excellence for Molecular Food Sciences, University of Belgrade - Faculty of Chemistry, Belgrade, Serbia.
authors.forename: Dragana
authors.initials: D
authors.lastname: Stanic-Vucinic
authors.affiliation: Center of Excellence for Molecular Food Sciences, University of Belgrade - Faculty of Chemistry, Belgrade, Serbia.|Department of Biochemistry, University of Belgrade - Faculty of Chemistry, Belgrade, Serbia.
authors.forename: Milan
authors.initials: M
authors.lastname: Nikolic
authors.affiliation: Department of Inorganic Chemistry, University of Belgrade - Faculty of Chemistry, Belgrade, Serbia.|Center for Computational Chemistry and Bioinformatics, University of Belgrade - Faculty of Chemistry, Belgrade, Serbia.
authors.forename: Milos
authors.initials: M
authors.lastname: Milcic
authors.affiliation: Center of Excellence for Molecular Food Sciences, University of Belgrade - Faculty of Chemistry, Belgrade, Serbia.|Ghent University Global Campus, Yeonsu-gu, Incheon, South Korea.|Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium.
authors.forename: Tanja
authors.initials: T
authors.lastname: Cirkovic Velickovic
mesh_terms: D001665:Binding Sites; D062105:Molecular Docking Simulation; D052980:Phycobilins / Q000737:chemistry / Q000494:pharmacology*; D010798:Phycocyanin / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding; D055550:Protein Stability; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism; D053545:Spirulina / Q000737:chemistry
chemical_list: D052980:Phycobilins; D012709:Serum Albumin; D010798:Phycocyanin; C011069:phycocyanobilin