Fig 1.
A) Ball and Stick representation of 4PBA; Carbon = Grey, Hydrogen = Cyan, Oxygen = Red b) Cartoon model of HSA-MYR complex (PDB: 2BXP) showing different subdomains and major fatty acid binding sites.
Fig 2.
a) UV-Vis spectra of HSA in presence of 4PBA. Cuvette concentration, cHSA: 1μM (a) and c4PBA (1,2,4,8,12,16,20 μM): b→h; pH 7.4 at 25°C. Inset shows slight blue shift at the Tryptophan absorption region indicated by the arrow. b) Effect of ethanol on the fluorescence emission intensity of HSA. cHSA = 1μM, cEthanol =, 1,2,4,8,12,16,20 μM (pH 7.4, 25°C) c) Fluorescence emission spectra of HSA in presence of 4PBA. cHSA: 1μM (a) and c4PBA (2,4,8,12,16,20 μM): b→g; pH 7.4 at 25°C.Dotted line represents contribution of4PBA (20μM) at the emission range of HSA. d) Plot of 1/F-F0 vs 1/ [4PBA]
Fig 3.
Ligand displacement assay of HSA with Quercetin, 4PBA.
a) Percentage initial fluorescence of HSA (at 345 nm) upon addition of 4PBA, Palmitic acid and Quercetin (2–20 μM). b) Binding of 4PBA and Quercetin at different sites. Tryptophan fluorescence of HSA was monitored at 345 nm in the presence of 4PBA. To HSA-PBA complex (of varying PBA concentration: 2–12 μM), Quercetin was added from 2–20 μM and c) To HSA-Quercetin complex (of varying Quercetin concentration: 2–12 μM), PBA was added from 2–12 μM. HSA fluorescence was normalized to 100% in the absence of added ligands.
Fig 4.
Displacement of Dansylglycine by 4PBA and Palmitic acid.
4PBA and Palmitic acid displacement of Dansylglycine. To HSA (1 μM) and Dansylglycine (1 μM) complex, 4PBA and Palmitic acid were added incrementally from 1–8 μM.
Fig 5.
Stability of 4PBA at FA binding sites of HSA.
a) Time evolution of RMSD of the HSA backbone and PBA bound forms during 7ns MD simulation of 4PBA bound to HSA at different FA binding sites. b) Interaction profile of 4PBA at all FA binding sites c) Salt bridge formation at FA3.
Fig 6.
Binding of 4PBA induces conformational changes on HSA.
a) RMSF of Cα atoms of Unliganded HSA (discontinuous black lines) and 4PBA bound HSA at different FA binding sites. The demarcations show different Subdomains of HSA. Significant fluctuations can be seen at Subdomain IA and IIIB; the most mobile and hydrophobic fragments of HSA. b) 2D projection of first two principal components of different 4PBA-HSA bound models. c) Spectrum of Eigenvalues vs Eigenvector Index. d) CD absorption spectra of HSA-4PBA complex (HSA-1 μM; 4PBA-1μM).
Fig 7.
Motion of Cα atoms for the extreme values of the principal components obtained from MD simulation trajectory.
a-f) represents the motion of Cα atoms of FA site 1 to 6- 4PBA occupied complex respectively.
Table 1.
MM-PBSA Binding Free Energy components of HSA-4PBA complex.
Table 2.
Total and Residue Hydrophobicity (SASA analysis).
Fig 8.
Dynamic Movement of W214 and descriptors of W214 pocket at HSA-4PBA complexes.
a) Shifting of W214 residue in different HSA-4PBA complex. b) Movement of W214 pocket descriptors upon 4PBA binding at different FA binding sites.
Table 3.
Residue hydrophobicity of descriptors of W214 pocket upon different FA site complexes (SASA analysis).